While we're waiting on California (and may continue waiting until tomorrow), it appears there's been some trouble with ballots in the state. A "crush of new independent voters" caused confusion at the polls, with poll workers not being clear on the rules about who could get a Democratic ballot, and voters not knowing that they had to ask for one. It's unclear how widespread the problems were, though. This of course affects just the Democratic primary there, as independent voters can't participate in the Republican primary. Since Obama has attracted more independent voters than Clinton so far in the primaries, this could possibly be a factor if things are close there.
--Kate Sheppard