Here's on of my favorite new projects, a custom clone of the venerable Big Muff fuzz effect pedal by Electro Harmonix. This pedal sounds good on guitar, but phenomenal on bass. Here's a video demo:
I made a couple changes to resistors to change the gain response and final output - I basically spent an evening on my couch with the breadboarded prototype of this pedal, switching resistors and seeing how I liked it.
There are lots of sites out there with the original Big Muff schematic, but I worked off the resources at www.generalguitargadgets.com. GGG is an incredible site - they have tons of info and also sell ready-to-solder effect kits and tons of parts. I opted to go with a fully DIY stompbox with an old school Radio Shack circuit board: shown below after the jump (with schematic info):
