Here's a cool bass fuzz designed by Derringer over on DIYSB. It's based around the classic DIY Bazz Fuss with built in blending circuit. Derringer mentioned that it might need a booster after it. The good ol' LPB-1 should do nicely. Just put it between the Blend pot and Volume pot. Here's the schematic.
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.