General Guitar Maintence/Repair:

Dan Elrewine's Book

Guitar Building:

http://www.projectguitar.com/
http://mimf.com/

Guitar Wiring:

http://www.guitarelectro...tegory/wiringresources/
http://www.stewmac.com/freeinfo/i-4000.html
http://www.guitarnuts.com/wiring/index.php
http://www.smitspickups.com/coiltapping.htm

Speaker Cab Wiring:

http://www.colomar.com/Shavano/2x12wiring.html

Affordable Guitar Parts:

http://www.guitarfetish.com/
http://www.dragonfireguitars.com/index.php
http://www.guitarheads.net/

DIY Pedal Kits:

http://www.buildyourownclone.com/
http://www.generalguitargadgets.com/
http://www.olcircuits.com/
http://www.paia.com/guitarfx.asp

General Electrical Parts:
http://www.mouser.com/
http://www.smallbearelec.com/home.html

ive also recently come across this in the UK

http://www.diyguitarshop.co.uk/

It was reccommended to me by a local luthier saying in the past he has constructed some of the stuff there for customers who cant afford a full custom and gave glowing reports on the quality of the timber and the general machine work.