Craigslist is definitely going to be your best choice for finding a rental.

I also found Backpage.com to be useful. I think the Reader classifieds show up here.

You can try the Union Tribune classifieds, although I never had much luck with them. But, should a place be listed by a non-technical person who doesn’t use the internet or doesn’t know about Craigslist, it’ll probably end up there.