The official court site is crashing because everyone in the world is hitting refresh at once and Twitter is awash in rumors that can't be confirmed, but New York magazine, the first reliable site I've seen with a report on this, says:

Big news: According to a source who has seen the 136-page decision, U.S. District Court Judge Walker has ruled Proposition 8, the California voter-approved ban on gay marriage, unconstitutional under both the due-process and equal-protection clauses. We're staying tuned and will report more details when we get them.

If true—and it's still a big if; I haven't seen the decision yet and it sounds like New York mag's blogger hasn't either—if it's true, this would be what gay rights lawyers and activists have described as the best possible outcome.

UPDATE: Freedom to Marry, one of the leading marriage equality groups in the country, seems to confirm this New York Mag report on its Twitter feed. As does Equality America.