One of the earliest DIY sites, Analog Music Zone, specializes in guitar effects and electronics. It has instructions for building all types of guitar effects, including clones of popular stompboxes.
This labor of love is put together by Jack Orman, a hardcore DIY enthusiast who’s also written extensively for magazines on building custom stompboxes.
The site is one of the most popular guitar-oriented DIY sites on the Net. Ormand provides circuits and articles on compressors, tube-distorition, big muffs, and even the mildly obscene G-Spot germanium overdrive. Analog Music Zone is probably the only site in the world where you can take a look inside the G-Spot.
AMZ also reviews guitar effects, and it’s obvious that the reviews are from somebody that knows his effects.