BoingBoing reader Gwen says,
http://www.nohr4437.org/ has listings for many May 1 rallies in protest of HR4437 and seeking amnesty for and tolerance toward immigrants. The site's awful, you have to scroll down for links to regional May 1 events info.
Here's a site specific to the SF Bay Area events.
Legal info for marchers: This new legal info site is for students who are being persecuted for asserting their rights, and includes info specific to high school students'/minors' rights in California.
the ACLU's Immigrant Marches info is here,
and printable Bustcard for the DIY Planner set is here.
