I have yet to find anyone cheaper than Osh Park for one off PCB fabrication. Though you can do better when numbers are higher, the usual supsects like ITead and Seeed have very good prices with a minimum quantity of ten. I've used Smart Prototyping before and they have very good prices similarly. Typically for a hobbyist you would not have need for more than one or two copies so Osh Park is going to be the cheapest option. If you're in the US the service is about the fastest you'll find. I have had boards turn around as fast as a week with them, but two weeks is more typical.
The industry standard is Gerber and Excellon plot files. If you're using software that is not able to produce those, you'll need to migrate to something that can. There was (is?) a trend for prototyping services to require use of their own in-house CAD software in an effort to lock you into their service. Typically their CAD programs use a proprietary file format and are not able to produce Gerbers. The software can be pretty good, Express PCB is one, but it's not a good thing to pigeon hole your designs like that. It's going to give you trouble at some point.