Here's a gallery from Seattle, two disturbing photos of extremists leading a San Diego march, and a slideshow from the Bay Area here.

UPDATE: There are several pics from the L.A. march here, including one from the Los Angeles chapter of the FMLN. That's a former El Salvadoran Marxist guerrilla group turned political party, which got 40% of the vote a few months back. At their site, they discuss a May 1 march in their country in support of their citizens in the U.S.: tinyurl.com/kv9xe

UPDATE 2: There's a video here.

UPDATE 3: There are a few videos from the other side here.