tesseract: (and anyone looking for a cheap bike) all imma say is check the trash. i have found so much good shit in peoples trash. the bike im riding now (fork, saddle, frame, brake, BB, cranks), a fairly nice road frame, and this motobecane im building up as a touring bike were all salvaged from various peoples curbs and bike shop garbage bags. theres a few shops i frequent weekly for random parts for beater bikes, but i get lucky sometimes too.
for instance, i just came across a 700c, 36 hole mavic open pro rim thats the red andonized jaun. as far as i can tell somebody blew up a hub and just bought a new wheel. some woman down the street from me was chucking out this old lime green cruiser thats in like new condition so thats going to a friend of mine. its worth it even for little dumb stuff like extra spoke nipples, hard to find nuts and bolts that get left on ruined frames, etc.
also, if youre in a metropolitan area, keep an eye on bikes that have been locked up for long periods of time and slowly begin to lose their parts. i would NEVER steal someones bike (just because i know how much time and effort goes into it), but im not opposed to borrowing a few things off of a bike that has been rusting away on the corner for a year where it has probably been abandoned.