NerdKits (http://www.nerdkits.com/). Started with roommate co-founder in senior year of college with $200 of parts, continued part-time while I still in school / doing Masters degree, and now full-time since graduation (almost a year and a half now). Profitable and a lot of fun.
Heh, I remember reading a shameless self-promotion post from you on Slashdot a few months back. Looks like things have turned out well, and I'm considering getting one myself. Nice work!
