Geo: Mods, pcbs layouts etc.

Smallbear electronics: All kind of electronic material to built your home-made boutique pedals!

Ampage Sound Samples: Sound examples of home-made pedals.

Pisotones: Fantastic web for the pedal DIYer. In Spanish.

The Tone God: Info about lots of well-known pedals.

Doug's Do-It-Yourself Guitar Effects Page: Mods for some of the most communly used pedals.

Homebrew Tweaks: More pedals for the DIYers!

Tonepad.com: Pedal layouts and an interesting forum.

Mark Hammer's Articles: Lots of Do-it-yourself articles about pedals.

Aron Nelson's Stompbox Page: Esential site for the pedal builder. Lots of info availble.

The Analog Music Zone: Vintage pedals layout.

GuitarElectronics: Electronics parts for your guitar.

Tonefrenzy: Boutique pedals.

Howard Davis: This guy designed some of the best Electro Harmonix effects. A good one to learn from!