I'm desperate...

Okay, so this is a shot in the dark but I'm desperate. Does anyone have any idea a good place to look for inexpensive tickets for show in San Fransisco? We're going to try to get tickets to Wicked while we're in California but I'm so bad at searching for things online and I just wondered if anyone knew of good websites. (Besides Ticketmaster. I'm not a big fan of them because they're kind of expensive.) Let me know as soon as possible if you have any ideas. We leave this Wednesday night. Thanks for any help you might have.