For Fuzz Friday here's a really cool circuit designed by Lubdar over on the Madbean forum. It's inspired by Death by Audio designs and can go from overdrive to full on fuzz. If you can't get a DBA design working, give this one a shot. Here's what he had to say about it:
It's a combination of ideas from the newer Evil Fuzz/Harmonic Transformer/Interstellar Overdriver.
It is comprised of 2 reverse beta gain stages, with level controls for each, that way you can turn level1 all the way down and get fairly clean overdrive tones, or max it out for fuzz, and anywhere in between. The density knob controls the input capacitance for thin treble all the way to bass bass bass. The toggles are for switching out a transistor stage in the 1st gain stage, and the second is an output pulldown resistor to give a slight volume boost.
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.