Depends on your timeline and your budget. My guess is you want this cheap and you don't mind waiting. In that case you should look at a PCB aggregator service, which combines your design with a bunch of others, sends it out as a single panel, then cuts it up when the panel comes back and ships out individually. These places include BatchPCB, DorkbotPDX, and....some others I can't remember right now.
There are also direct-from-China manufacturers like Seeedstudio's Fusion service, ITeadStudio also has a similar service I believe, and Gold Phoenix has a pretty good deal on complete panels which you can fill up with as many of your designs as will fit for a single price (and you can start your own aggregator service!)
Things to look for: design rules. Ideally, you started your PCB design with an eye towards your board manufacturer's design rules (minimum trace width, minimum space between traces, minimum hole/via size, etc.) If not, make sure you know what the design rules are so you don't get set back.
Other things to look for: look at your files before they do. Once you generate your Gerbers use a free viewer like GC-Prevue (gerbv for Linux/Mac) and make sure there are no surprises. Don't use silkscreen that is thinner than about 0.006" else it might disappear in manufacturing (or look really bad).
The Rugged Audio Shield: Line In, Mic In, Headphone Out, microSD socket, potentiometer, play/record WAV files