Migration of Grey Whales (seasonal North & South)

http://www.oceanicsociety.org/graywhales

Cinco de Mayo San Francisco

http://www.carnaval.com/sf/cinco_links.htm

San Francisco Documentary Film Festival

http://www.sfindie.com/

SF Bike to Work Day

http://www.sfbike.org/?btwd

Bay to Breakers (a 12k / 7.46 mi race through the streets of San Francisco)

http://www.baytobreakers.com/main.html

Asian Heritage Street Celebration

http://www.asianfairsf.com/

Carnaval San Francisco

http://www.carnavalsf.com/

The San Francisco Natural History Series

http://sfnhs.wordpress.com/

Critical Mass Bike Ride

(begins at east end of Market St on the last Friday of the month at about 6pm)

http://critical-mass.info/