Links

Guitar repair

• Frets.com - Pretty much every kind of repair you could think of with lots of pictures and tricks.
• Guitar Refinishing at the ReRanch

Tube amps

• The Valve Wizard - good info on understanding tube amp circuits. The Common-cathode triode gain stage article is especially good for learning how amps are designed.
• AX84 - Several original amp projects and a good support forum.
• Fender Field Guide - details and schematics on vintage Fender amps.
• Ampage layout tips
• RCA Receiving Tube Manual - Several PDF's of the various RCA manuals are floating around out there, they're very helpful. The older versions (RC-14) have data on some very old tubes.
• Master volume controls - a nice bit on Mike's tube amp pages on various MV techniques.
• This is a nice tutorial on setting up LTspice to model a tone stack.
• T's tech notes - notes about tremolo circuits, etc.

Miscellaneous

• Delta Blues Tips - best acoustic blues lessons ever.