I built couple of frames, it is not such a big deal, but if you want to just build one, even with minimum tools, the cost is not really worth it. It is not particularly hard, especially if you silver/brass braze lugged steel bike. It is time consuming while you are learning, without fancy jigs, etc. (I did mine with hack saw, files and Dremel) but it is certainly very posible and lot of people are doing it. I enclose couple of links:
http://www.sheldonbrown.com/rinard/framebuild.htm and
http://www.phred.org/~josh/build/suppliers.html
I don't have any links for recumbents, but do a google search, there are many folks building them and I believe I even saw some kits for sale. I also remember seeing some fellow building a Carbon Fiber frame from scratch, in Germany somewhere, so do the search....