I am seriously hooked on building my own synths and effects now. The modular approach to sound design is really engaging, and the fact that I have to build the modules myself means that I’m willing to invest much more time in using them than some of the modern digital gear.
I found a great site – Music From Outer Space – full of module plans and designs for effects units.
I’m going to be following some of the designs and slowly putting together a modular synthesizer in an old piano cabinet I have at home.
Another great site is this one Tonepad – guitar FX schematics and designs.