A video from Nate McCoy documenting the making of a MIDIBox SID.
The MIDIBox SID is a DIY synthesizer, based off of the MOS Technology SID sound chip, the 8-bit sound source of the Commodore 64 computer.
More information on the MIDIBox SID:

http://www.ucapps.de/
http://forum.midibox.org/
http://www.midibox.org/dokuwiki/
http://www.avishowtech.com/mbhp/buy.html

Demo videos of the MIDIBox SID.

http://youtube.com/watch?v=lnTh4e0b-ic
http://youtube.com/watch?v=FrgdErwTJ5o

The MB-6582 is a four channel stereo synth (8x 6582 SIDs) diy project. More photos here.
Here’s a video of the MB-6582 in action:

Synth fans: Don’t watch this video of the MIDIbox SID Bassline unless you’re ready to lust after something that can’t be bought:

You can build one, though. The MIDIbox SID, based on the Commodore 64 sound chip, is a very cool DIY project.