I just finished my x0xb0x synth. It is a Roland TB-303 clone which was originally developed (or reverse engineered) by Limor Fried at adafruit. The kit I built was from willzyx.com.
The timelapse video below shows the complete build. It took me about 10 hours to complete the synth, and luckily it worked straight away.
I am sorry about the rubbish soundtrack in the video. It was just about the first sound coming out of the box recorded and produced live in a really amateurish way (in other words, it is DIYcrap).
Anyway, it was a really fun kit to build. Although the kit consists of more than 500 components, it is fairly simple to build as long as you keep everything in order. All parts came in clearly labeled bags and not a single piece was missing from the kit. Willzyx is highly recommended!