Friday, 9/27 is the tenth anniversary of the Critical Mass bike ride that started in San Francisco. 10 years later, it's still going strong and has spread to over 300 cities. People are meeting on Friday at 5:45pm at the foot of Market St. in downtown for the anniversary ride, ending at Church and 20th. The anniversary is fortunately during the last half of September, which the excellent folks at Car Busters have declared as World Car-Free Days. The city of San Francisco has sort of announced its first Car-Free Day on the same day as the anniversary ride. Announcements were sent out to inform people that Montgomery St. will be closed between Market and California from 10am to 2pm. Bike for Colombia, a mobile spoken word performance protesting the "Plan Colombia" oil war , will meet in front of Chevron-Texaco at 4:30pm (575 Market between 1st and 2nd) and merge with Mass at 5:45pm. Tune in to a live microradio "Critical Broadcast" at 87.9 FM.