International Female Ride Day is an annual event that occurs the first Friday of May. This year, the event is Friday, May 4th. The event is organized at an international level, but celebrated on a local level with grassroots groups organizing their own local rides and events.To participate, women can join with other local women and get out and ride!
UPDATE: Women on Wheels is running a photo contest for the most creative photo taken on International Female Ride Day. For more info, see this Pdf document