if you've ever thought about creating your own musical instruments, you have to check out "the musical instrument makers forum". this online forum has plans, ideas, construction tips and other goodies to support you as you build an instrument. if you want to build something from a kit, i highly recommend checking out "musicmaker's kits, inc". they have a large selection of instruments that range in difficulty from easy to hard. i've purchased supplies from them in the past. they have an excellent catalog that they send out quarterly.
finally, i found a really cool site maintained by dennis havlena that has a bunch of free plans for making instruments like a bass guitar out of a washtub (not the old broomstick kind, but rather a real 4 string standup bass guitar). his site is a wealth of information for diy'ers.