The Bleepotron is a MIDI synth kit that uses a dsPIC digital signal processor. It's a very easy build and has a great lo-fi sound. It's even possible to edit patches and save on it!
I housed mine in an old vid box.
I ran through all it's presets sounds here.
(sorry about the crap loop)
More info about it below...
Bleep-o-tron has the following features:
• 2 x oscillators (timbres)
• 8 x phase-modulation waveforms + combinations (36 in total)
• white noise
• 6 x ADSR (attack-decay-sustain-release) envelopes
• 6 x LFO’s (low-frequency oscillators)
• 6 x LFO waveforms (sine, square, triangle, rising sawtooth, falling sawtooth, noise)
• detuned second oscillator by octaves, semitones or cents
• connects to standard MIDI keyboard (velocity sensitive)
• keyboard transpose (up to +/– 2 octaves)
• keyboard split
• play notes using PS/2 PC keyboard
• pitch bend and modulation using PS/2 PC mouse
• ring modulator
• oscillator synch
• flanger (swept comb filter)
• portamento (constant rate and constant time)
• selectable MIDI channel #1 to #16
• 16 x preset patches
• 8 x user patches (non-volatile)
• master volume control + gain x 2