Effects pedals are a great introduction to the world of DIY guitar gear, because:
- The parts and tools required are relatively cheap
- The tools are relatively safe (you might burn yourself with the soldering iron though!)
- You don't need a special workshop - you could make most things on the kitchen table
- Project can be finished in a short time and are not too messy
- They use low voltages (if you wire your project up wrong you won't kill yourself)
Super-freq has got some great articles with free circuit diagrams for boost, delay, distortion, octave Up and overdrive pedals.
They also sell (for $4) a prototype PCB designed to speed up the process of making effects pedals by providing all of the standard wiring. This PCB contains the standard wiring for the in/out jacks, DC power with a reverse polarity protection diode and stompswitch. It also provides a perfboard area for building your effect. It’s designed to drop into a “B” sized box and leave room for a 9V battery.