August

Twilight at the Top Ride with docents Adda Quinn and Jen Basiji along two of the best single-track horse rides on the peninsula. Fri, Aug. 18, 3:30-8pm. Reservations required. Windy Hill Open Space Preserve, Portola Valley, 650.691.1200.

Cool at the Top Learn how Mountain View got its name on this 5-mile hike with docent Bob Segalla. Sat, Aug. 19, 11am-3pm. Monte Bello Open Space Preserve, Page Mill Road, Palo Alto, 650.691.1200, www.openspace.org.

Day's End Hike Bring a dog for this early evening 4.5-mile hike along the trails of Fremont Older with docent Mary Ann Frank. Sat, Aug. 19, 6-8pm. Reservation required. Fremont Older, Prospect Road, Cupertino, 650.691.1200.

High Trek Adventure Teams of two find clues to checkpoints on foot and using public transportation. First prize winners receive two plane tickets to anywhere in the continental United Staes. Aug. 19, noon. $150 per team. Metro City Bar and Grill, 3600 16th St, San Francisco. www.hightrekadventure.com.

Race Through the Redwoods A 10K race through Henry Cowell State Park with the start and finish at the main picnic area. Plus a kids' mile. Visit www.active.com to register. Sun, Aug. 20, 8am. $10-$20. Henry Cowell Redwoods State Park, Hwy 9, Felton, 831.335.7077.

Manatee Open Water Relay Swim Now in its 20th year, this relay swim involves teams of two members in various age divisions. Visit www.active.com to register. Sun, Aug. 20, 8:30am. $45. Quarry Lakes Park, 2250 Isherwood Way, Fremont.

Fort Point Promenade 12K A scenic 12K course along Marina Green to Fort Point and back. Visit www.dse runners.com for more information. Sun, Aug. 20, 9am. $5, 415.978.0837. Aquatic Park, Jefferson and Hyde streets, San Francisco.

Hook and Ladder 10K This race is in its 27th year. Visit www .active.com to register. Sun, Aug. 20, 9am. $20. Golden Gate Park, San Francisco.

Slumbering Giant Join docents Keith Johnsgard and Jack Daane on a leisurely 1.7-mile stroll atop the now-silent San Andreas Fault. Sun, Aug. 20, 2-4:30pm. Los Trancos Open Space Preserve, Page Mill Road, Palo Alto, 650.691.1200.

Scenic Aerobic Hike Join docents on a 4- to 5-mile hike around the preserve. Wed, Aug. 23, 10am-noon. Saratoga Gap, Skyline Blvd (Hwy 35) and Hwy 9 intersection, Saratoga, 650.691.1200.

Saratoga Gap Loop Greet the morning with docents Mary Bernstein and Barbara Patterson on this 6-mile loop hike. Sat, Aug. 26, 8:30am-noon. Saratoga Gap, Skyline Blvd (Hwy 35) and Hwy 9 intersection, Saratoga, 650.691.1200.

SEF iWALK For An Eye 2006 A fundraising 5K and 10K run and walk with proceeds benefiting the Sankara Eye Foundation. Visit www.active.com to register. Sat, Aug. 26, 9am. $15. Shoreline Park, 3070 N. Shoreline Blvd, Mountain View.

Russian Ridge Ramble Join docent Strether Smith for this intermediate bike ride at Russian Ridge Preserve. Sat, Aug. 26, 10am-2pm. Russian Ridge, Skyline Boulevard and Page Mill/Alpine Road, Palo Alto, 650.691.1200, ext. 526, www.openspace.org.

Ana Cable Car Chase A 5.67-mile run through the heart of the city, all the while chasing a cable car. Visit www.active.com to register. Sun, Aug. 27, 8am. $28. Aquatic Park, Jefferson and Hyde streets, San Francisco.

Mount Madonna Challenge A 12K race and 6K walk and run. Visit www.active.com to register. Sun, Aug. 27, 8:30am. $13-$18. Mount Madonna County Park, Gilroy.

Woods and Wine Wandering Join docents Tommi and Strether Smith for a 4-mile, moderately strenuous hike at the ranch, with the option of tasting at the winery. Sun, Aug. 27, 10am-2pm. Picchetti Winery, 13100 Montebello Road, Cupertino.

Lions and Us Docent Keith Johnsgard leads this 3.5-mile round-trip natural history hike, discussing and answering questions relating to mountain lions. Sun, Aug. 27, 11am-2:30pm. Skyline Ridge Open Space Preserve, Skyline Boulevard and Page Mill/Alpine Road, Palo Alto, 650.691.1200.

September

Alcatraz Swim With the Centurions This fundraising event for local breast cancer agencies and the U.S. National Parks Conservancy is in its fourth year. Visit www.active.com to register. Sat, Sept. 2, 9:30am. $75-$100. Alcatraz Island, San Francisco.

Seacliff Beach Trail Run From Seacliff State Beach, this 14K, 22K, 35K or 50K run heads through the Forest of Nisene Marks State Park and returns to the beach. Visit www.active.com to register. Sun, Sept. 3, 8:30am. Seacliff State Beach, State Park Drive, Aptos, 831.685.6444.

Potrero Hill Run A 4-mile loop course, half flat and half uphill with a downhill finish. Plus a free kids' half-mile run. Visit www.active.com to register. Sun, Sept. 3, 9am. $5. Potrero Hill, 17th and Arkansas streets, San Francisco.

Bras for the Cause A breast cancer research fundraiser walkathon. Visit www.active.com to register. Fri, Sept. 8, 8pm. $50. Thomas Hart Middle School, 4433 Willow Road, Pleasanton.

The Triathlon at Pacific Grove With both Olympic distance and spring distance options. Visit www.tricalifornia .com for more information. Sat, Sept. 9, and Sun, Sept. 10. Lovers Point, Pacific Grove.

Contra Costa Ride to Emmaus A 50-mile bike ride through Contra Costa County. Visit www.active.com to register. Sat, Sept. 9, 8am. Episcopal Church of the Resurrection, 399 Gregory Lane, Pleasant Hill.

Guts and Glory A 5K walk benefiting the Crohn's and Colitis Foundation of America. Sat, Sept. 9, 8:30am. Shoreline Park, 3070 Shoreline Blvd., Mountain View. 415.356.2232.

Intro to Outdoor Rock Climbing Full day workshop to learn skills like knot-tying and proper equipment usage. Instruction in the morning, then climbing in the afternoon. No experience necessary. Sept. 9, 8am-4pm. $95. Castle Rock State Park, Skyline Blvd, Saratoga. www.mtadventure.com.

Bike Against the Odds Ride for breast cancer research, with 100-mile, 65.6-mile, 47-mile, 30.2-mile and 12.2-mile options. Visit www.breastcancerfund.org for more information. Sun, Sept. 10.

Run to Remember 9-11-01 A 5 and 10K run preserving the memory of 9/11. With guest speakers and awards. Visit www.active.com to register. Sun, Sept. 10. $35-$40. Downtown San Francisco, Embarcadero at Folsom Street, San Francisco.

Big Kahuna Triathlon A long-course triathlon with a 1.2-mile swim, a 56-mile bike and a 13.1-mile run. Proceeds benefit the Leukemia and Lymphoma Society. Visit www.active.com to register. Sun, Sept. 10, 7am. $20-$75. Santa Cruz Main Beach, Santa Cruz.

Lake Merced Run A paved 46-mile loop around Lake Merced, plus a half-marathon loop course. Visit www.active.com to register. Sun, Sept. 10, 8am. $3-$10. Lake Merced, Sunset Blvd and Lakeshore Dr, San Francisco.

Baylands FrontRunners Run for the Community Both 5K and 10K runs of a flat, USATF-certified loop course around the baylands. Visit www.active.com to register. Sun, Sept. 10, 9am. Baylands Athletic Center, 1900 Geng Road, Palo Alto.

Franklin Memorial 10K Run Plus a 5K run/walk. This event was established in memory of the 87 Franklin employees lost during Sept. 11. Visit www.active.com to register. Sun, Sept. 10, 9:30am. $20-$25, 650.312.4200. Franklin Templeton Corporate Campus, 1 Franklin Parkway, San Mateo.

Back to School Scholarship Run With a 10K race, 5K walk and run and children's mile. Visit www.active.com to register. Sat, Sept. 16, 8:30am. Shadow Cliffs Regional Park, Stanley Boulevard, Pleasanton.

Tri for Real All of the Tri for Fun events lead up to this triathlon, with a 700-yard swim, 18-mile bike and 4-mile run. Visit www.active.com to register. Sun, Sept. 17. Shadow Cliffs Regional Park, Stanley Boulevard, Pleasanton.

Michelle Mazzei Memorial Family Bike Ride A ride in memory of teacher Michelle Mazzei. Visit www.active.com to register. Sun, Sept. 17, 8am. $10-$25. Oak Knoll School, 1895 Oak Knoll Lane, Menlo Park.

Banana Chase 5K and 10K Whole Foods and Jamba Juice sponsor 5K, 10K and children's races to benefit the UCSF Children's Hospital and Pediatric AIDS research. Sun, Sept. 17, 9am. Kezar Stadium, Golden Gate Park, San Francisco.

Single/Double Muni Pier Runs An out and back course along Aquatic Park with single loop and double loop options. Visit www.dserunners.com for more information. Sun, Sept. 17, 9am. $5. Aquatic Park, Jefferson and Hyde streets, San Francisco.

End of Season Camp A 270-mile, scenic bike ride from Sunnyvale to San Luis Obispo. Must be able to handle multiple days of 5-hour rides. Cost is $400-$550 and includes hotel and restaurant arrangements, on road services and ground support vehicles. Sept.22-24. www.active.com.

Founders Day Run A run benefiting Willow Glen Middle School PTA, Lucille Packard Foundation and Willow Glen Business and Professional Association. Visit www.active.com to register. Sun, Sept. 24, 8am. $10-$30. Downtown Willow Glen, San Jose.

Running of the Bulls 5K Costumed runners chase participants through the streets of Palo Alto. Plus a kids' "Running of the Calves." Visit www .active.com to register. Sun, Sept. 24, 8am. $15-$35. Peers Park, 1899 Park Blvd, Palo Alto.

Santa Cruz Sentinel Triathlon A triathlon with a 1.5K swim, 40K bike and 10K run. Visit www.active.com to register. Sun, Sept. 24, 8am. $99-$110. Santa Cruz Main Beach, Santa Cruz.

Six-Hour Distance Classic Run around the .8-mile dirt track as many times as you can in a six-hour period. Visit www.active.com to register. Sun, Sept. 24, 8am-2pm. $7-$15. Golden Gate Polo Fields, San Francisco.

Trailblazer 5 and 10K A 5 and 10K race and 5K trail walk. Visit www.active.com to register. Sun, Sept. 24, 8:30am. $15-$25. Microsoft Corporation, 1065 La Avenida St, Mountain View.

Almaden Times Classic A 10K and 2-mile run on a fast, paved creek trail and residential streets. Proceeds benefit the Almaden Valley Counseling Service. Visit www.active.com to register. Sun, Sept. 24, 9am. $12-$60. Leland High School, 6677 Camden Ave, San Jose, 408.268.6343.

Alcatraz Invitational Swim An annual 1.25-mile open-water swim fundraiser for South End Rowing Club. Visit www.south-end.org for more information. Sat, Sept. 30. 415.776.7372. Alcatraz Island, San Francisco.

Indian Health Center Quicksilver Challenge Half Marathon, 10K, 5K A scenic run through Almaden Quicksilver County Park in South San Jose. Sept. 30, 8am. $30. Castillero Middle School, San Jose. www.quicksilver-running.com.

October

Surf City Classic A ride with 25-mile, 60-mile and 100-mile options through Santa Cruz, San Benito and Monterey counties, with proceeds benefiting the Santa Cruz AIDS Project. Visit www.active.com to register. Sun, Oct. 1, 7am. $30-$40. Cabrillo College, 6500 Soquel Dr, Aptos, 831.479.6100.

RCP Tiburon Mile Athletes swim one nautical mile to downtown Tiburon, with proceeds benefiting Special Olympics Northern California-Marin. Visit www.rcptiburonmile.com to register. Sun, Oct. 1, 9am. $69-$200. Angel Island State Park, 120 Main St, Tiburon.

Rock & Roll Half Marathon Visit www.active.com to sign up for this half marathon run and rock. Sun, Oct. 8. San Pedro Square, San Pedro and Santa Clara streets, San Jose.

Rock & Roll Half Marathon This "musical marathon" is a 13.1-mile race beginning at HP Pavilion and ending at Plaza de Cesar Chavez. Sun, Oct. 8, 8am. $55-$85. HP Pavilion, 525 W. Santa Clara St, San Jose, 408.998.TIXS.

Volvo Best Buddies Challenge Maria Shriver, Cindy Crawford and Carl Lewis race in this 100-mile, 62-mile and 15-mile ride, with proceeds benefiting Best Buddies International. Call or visit www.bestbuddies.org for more information. Sat, Oct. 14. 800.718.3536x60. Chateau Julien Wine Estate, 8940 Carmel Valley Road, Carmel, 831.624.2600.

Waterfalls of Big Basin A run through redwoods and past waterfalls with 16-mile, 10.5-mile and 5.5-mile options. Visit www.redwood trails.com for more information. Sat, Oct. 14, 9am. $29.95-$39.95. Big Basin Redwoods State Park, Hwy 236, Boulder Creek, 831.338.8860.

10th Annual SuperKid Triathlon Register online at active.com. All finishers receive a medal. Races in varying age groups. Sun, Oct. 15, 7am. $33. Simpkins Family Swim Center, 979 17th Ave, Santa Cruz, 831.454.7966.

Half Moon Bay Pumpkin Run 2006 Register online at active.com. 5K run, 5K walk and 10K run. Sun, Oct. 15, 8am. $25. Hatch Elementary School, 490 Miramontes Street, Half Moon Bay.

AlcaTRI XXVI The 26th annual Escape From the Rock triathlon includes a 1.5-mile swim, 2.5-mile run, 13-mile bike and 7.5-mile run. Visit www.active.com to register. Sun, Oct. 15, 9am. Alcatraz Island, San Francisco.

Happy Fish Run for Education A 5K and 10K run around the lake, plus 0.5- and 0.25-mile runs for kids. Proceeds benefit the Fremont Education Foundation's Guy Emanuele Sports Fund. Visit www.active.com to register. Sun, Oct. 15, 9am. $10-$25. Lake Elizabeth, Central Park, Fremont.

Silicon Valley Marathon Marathon, half marathon, 5K run/ walk or kid races start in downtown San Jose. Pasta party the previous evening for the first 300 registrants. Oct 29. 408.295.9600.

Send a letter to the editor about this story.