For theater and teaching work, I check the Theatre Bay Area website (members only). I also look for theater jobs at the Actor's Equity website (free to look at) and did that even before I was a member of Equity - some projects are casting both Equity and non-Equity actors, and there'll be more info at the Equity site than TBA.
For on-camera projects, I look at SFCasting (members only), Now Casting (free - but you have to create a profile), and the Reel Directory Production Hub page (free).
And then there's craigslist. Acting work is posted in two places on the craigslist site. Under 'jobs' there's a classification tv/film/video. Any work you find here should be paid work - if they aren't paying, flag it as miscategorized. Under 'gigs' there's a classification 'talent'. And what's here is the wild west of jobs. I have found legit projects here that paid a few thousand dollars, and I also see a lot of scams and opportunities to be photographed or filmed w/no clothes on. A few warning signs to watch for w/craigslist:
- when 'a major hollywood casting company' is casting 'lead roles' in a blockbuster film or top 10 tv show at an 'open call' especially when that film is already showing trailers in the theaters.
- the phrase 'no experience required' - often this is because the people making the project have little to no experience themselves. Or they just want you to take your clothes off.
- really short casting timelines for independent/no-budget film. For commercials, the casting often happens really quickly, but if you're shooting an indie and you're organized, you've probably been planning to shoot for weeks if not months, and therefore did casting a while ago. If the ad says 'we're shooting tomorrow and need an actress' you can expect disorganization
- phrases like 'open-minded' or 'must be really really hot' or a lot of emphasis on physical attributes. Again, they probably just want you to take your clothes off.
- anything that requires you to sign up for a profile at another casting site in order to be considered for the project. They probably don't have a project, but just want to collect your name and email address for their site to sell you some kind of service.