Here's the most from-scratch one I did, the MIDIbox SID-NUXX, which is a completely custom reimplementation of the MIDIbox SID. Custom mainboard PCB, front panel PCB, enclosure, everything.
I had the Gerbers up for download under CC-Non-Commercial license until someone started selling devices based on it on eBay.
The guy who asked people to post their homemade instruments, 13strings, is a total idiot. He attempted to achieve fame and glory (well, the youtube kind) by building a bass with what he thought was the most strings any bass has ever had (13). He didn't bother to read up on how to make a bass, or even how to tune one, put it together with tape, and tried to sell it for like 3 grand. He also has a totally bizarre accent.
Checkout the Josh Dion Band on 3/21 at the Bowery Ballroom! Also see live concert footage of the Josh Dion Band from the Bitterend on 3/12 only at woozyfly.com!!