Here are a bunch of schematics, primarily for guitar effects, with some other stuff thrown in. (I use Microsoft Visio for all my technical drawings, including schematics.)
Learn more about reading schematics here: From Schematic to Reality
Alembic Stratoblaster Schematic
Apollo Treble Booster Schematic
Beavis Audio FKR 2.1 Schematic
Beavis Audio Noisy Cricket Amp Schematic
Beavis Audio Trotsky Drive Schematic
Colorsound One Knob Fuzz Schematic
Colorsound Overdriver Schematic
Dallas Fuzz Face (PNP, Positive Ground) Schematic
Dallas Fuzz Face (NPN, Negative Ground) Schematic
Dan Armstrong Blue Clipper Schematic
Dan Armstrong Green Ringer Schematic
Dan Armstrong Orange Squeezer Schematic
DOD 440 Envelope Filter Schematic
Dunlop Fuzz Face JH-1 Schematic
Electro-Harmonix Big Muff Pi Schematic
Electro-Harmonix LPB-1 Booster Schematic
Electro-Harmonix Muff Fuzz (Opamp Version) Schematic
Electro-Harmonix Muff Fuzz (Transistor Version) Schematic
Frank Clarke's IRF 510 MOSFET Power Booster Schematic
Hemmo BazzFuss Single Transistor Fuzz Schematic
Hornby Skewes Treble Booster Schematic
ProCo Rat II Distortion Schematic
Smokey LM386 Cigarette Amp Schematic