If you’re thinking about having any PCBs manufactured, either for your own projects, or for commercial work, I can very highly recommend the www.oshpark.com service based out of Portland, OR. Boards are manufactured in the US and come with ENIG gold finish standard.
You pay by the square inch ($5/inch for 2-layer, $10/inch for 4-layer) which for smaller designs can be quite ludicrously cheap compared to direct services. You get 3 copies of your board, and in my experience delivery times are around 2 weeks for 2-layer boards, and 2.5 - 3 weeks for 4-layer (they generally quote longer). The web interface is truly great providing digital mockups from your Eagle, or Gerber files so you can visually check that everything looks right without the need for a good CAD viewer. In general the process is automated very effectively and feels quite seamless.
All the eurorack modules I’ve had a part in have been prototyped with this service with largely no complaints. I’ve had great success making tiny 1" boards to replace hand-wired programmer adaptors. Furthermore, the relatively low price for 4-layer boards allowed me to experiment with layout techniques (ground & power planes in particular) that I was previously afraid to even consider.
As you get 3 copies of a PCB whenever ordering a design, perhaps you’d like to offer any extras below either built or otherwise.
