Several thousand protesters are marching on the Bay Bridge as we speak. According to a call-in from a cell-phone, things have just started getting "out of control"... police don't know what to do to stop the protesters. 3-4 onramps have been taken over by protesters.
You can read the updates at http://sf.indymedia.org or listen live via a pirate radio station that has been set up -- "Enemy Combatant Radio" is on the air, broadcasting over the web and across San Francisco at 93.7 FM.