On the last Friday of every month, cyclists around the world gather to ride the streets together to assert the rights of non-automotive traffic to use the streets.
In Calgary, we meet at Eau Claire (near the Olympic arches and the YMCA). The rides usually leave no later than 6pm, and take a generally random route (determined by the riders) through downtown and sometimes into other inner-city communities.
September is often the last big ride of the year (since many folks stop coming once there's snow and salt on the roads). So, come out and celebrate bicycles!
Official Website: http://criticalmass.meetup.com/15/
Added by Grant Neufeld on September 17, 2006