There is only one company I'm aware of that provides them at prices a hobbyst can flip a bunch out and not worry:
http://www.pcbway.com/orderonline.aspxBoards actually seem to come out alright, just don't expect absolute perfection.
For better quality stuff that doesn't break the bank, oshpark seems to come up over and over again, and Circuit Labs here in NZ is worth a look also. I haven't had any boards made, but spent a lot of time sniffing around on the subject myself.