In the USA, it's usually hard (but by no means impossible, depending on your needs) to beat the Advanced Circuits $33/ea deal on 2-layers, especially if you have multiple designs to pool together ($50 panel fee extra but then crank it all the way to 70 sq in). Minimum order is 4 + $10 handling = $142 for the lot, and the specs and quality are very good and consistent, and they ALWAYS ship them on time (often early). Their CAM guys are pretty thorough, too. Especially for a newcomer, they'll very often catch stuff that the cheaper services will totally gloss over and run "as is" in unusable condition. If you're a "student" (and they do have some verification), the minimum on the $33/ea deal is 1, which is almost impossible to beat even with the hobbyist services except for very small designs.
If you really do need it cheaper, you're probably going to be stuck with a hobbyist/batch service. The results vary and turn time is usually longer, but I've heard of people getting them down to about $15-25 total lot charge for a (small) board.
http://oshpark.com/ is about the best deal I know of with good specs. They're cheaper than the Advanced Circuits service for anything less than ~25-30 square inches (though you only get 3 boards), and you get ENIG and can have slots which Advanced Circuits doesn't allow on their $33/ea deal.
I recommend running your files through the Advanced Circuits freedfm.com regardless. They catch all sorts of things in that (mostly automated) check, even a few things my ECAD package misses (my ECAD package also checks a bunch of stuff they don't, too, so I always run both).
I place $33/ea panel orders somewhat frequently. If you don't need something for the next several months and can afford to wait until I make an order, I may be able to throw you on a panel with some other stuff for little cost.