Lofi instruction manuals for current BugBrand devices - all in pdf format:
BabyBugCrusher9v Instructions
AudioWeevil06 Instructions
Weevil07 Instructions
Weevil06 Instructions
PostcardWeevil Instructions

Venn Festival Build Your Own Light Oscillator Workshop:
Workshop Guide - covers the theory & design of a simple 555-based electronic oscillator, plus circuit building background.
Building Guide - how to build the circuit using the PCB.
PCB image - for making the circuit board (300dpi image giving 8.4 x 5.9 cm sized board)

Bring Yourself Festival Circuit Bending Workshop:
Workshop Guide - an introduction to circuit bending covering techniques, tools, components, etc.

Circuits, Bending, Electronics, Effects:
Experimentalists Anonymous - a great site for DIY devices, with a discussion forum and extensive schematic archive.
Aron Nelson's Stompbox Page - one of the best places for stomp box design, with vast archives, guides and a forum.
General Guitar Gadgets - many excellent guitar effects projects.
Geofex - DIY guides, schematics, etc
Runoffgroove - great site with schematics that emulate classic amp designs.
Commonsound - audio electronics cooperative collection with extreme device design.
John Hollis (Guitar Effects), John Hollis (Circuit Bending) - interesting designs and a great circuit bending info page.
AntiTheory (Reed Ghazala - early circuit bending pioneer.
Oscillateur.com - details of Speak & Spell bending.
Paia - long running DIY audio electronics company with lots of info dotted around the site.
Cloned Analog Gear - many old electronic magazine articles for DIY audio machines.

Electronic Component Supplies:
Rapid Electronics - the most highly recommended supplier in the UK.
Small Bear Electronics - excellent US based company with lots of hard to find guitar effects components and a bunch of info.
Digikey - large US based supplier, good for certain things (eg voice recording chips).