Thank you, I've never seen a PCB assembly service, so that will be useful. I guess one would also need to design some sort of cover as well and talk to a company that makes plastics? Are there plastic assembly companies as well (for if your product has buttons/sprints/etc)?
There's Protomold[1] which does relatively cheap short runs of plastic manufacturing. I'm sure there are plenty of alternatives (and I recall seeing a massive chinese 3d printing contract manufacturer, but forget the name).
Not sure about assembling all the parts into the case. Depending on who does the PCB production and assembly, they might also offer a full assembly service, or not.
The Factory Floor series[2] by Bunnie Huang might be an interesting read about some of the steps necessary for getting an idea to production.
This looks great, thank you. They're still prohibitively expensive for small runs (for 10 boards, above, the cost was $100/board, but for 1000 it fell down to $2/board, and I'm sure protolabs is similar), but at least your comment and the GP takes me from "I wouldn't know how to even begin making this thing" to "Looks like I can just send these guys designs and my box prototype and get assembled PCBs and boxes back", which is almost there, pretty much.