MAKE:blog reports on a build-your-own synth project that could be just advanced enough to be interesting, just simple enough that you’ll get through it without a disaster:
Sound Lab Mini-Synth [Music from outer space]
Looks perfect — a simple but capable design. And if for some bizarre reason this is too easy for you, you might customize it with something trickier like an LED-lit envelope generator or one of the fellow’s other kits.
Good additional resources:
The latter has kits for vocoders, tube preamps, and lots of other goodies.
So, has anyone out there built a DIY synth? Let us know how it went, and send photos / sounds / anecdotes.