decent setup, or you could also make do with a webcam and a flat surface, but, if you're looking for something with a smooth feel on the cheap, the solution is the hard drive sitting in your closet that's too small even for backup duty. A group of students at universities in the UK, Austria, and New Zealand all worked together to come up with a homebrew digital DJ interface, and the above HDD-cum-turntable sits at the center. The weight of the disk plus the quality of its bearings won the crew over, and with "a few op amps, resistors and a programmable microcontroller of some kind" you too can be mixing in no time. Full instructions are at the read link, and check out the video below for a little platter-scratchin', oscilloscope-watchin', "wicky wicky" action.
[Via Hack A Day]