Here is a list of independent Electronic Kit makers. I try to keep this updated often but its certainly not complete.
I don't consider these companies to be independent kit makers but I include them for completeness' sake
Music & MIDI Kits
RF (Radio) Kits
sells all sort of kits for ham radio and other RF meddling
a complete reproduction of the 8800!
Electronic Enigma (WWII cypher) machine kit
Embedded Projects Shop
sells a USB AVR programmer (Warning: you need a programmer in order to make this kit work, a real catch-22)
make a nifty little oscilloscope vector clock kit
Makes some basic 4 & 6 nixie tube clock kits
Neat alarm clock kit that, well, just don't take it to the airport with you