Public landfills. I was dumping some junk on Saturday and saw some cases in the "office crap" area and looked them over. One looked like a fairly new Dell, so after a quick inspection I scooped it up and put it in the trunk of my car. (I'm not sure if it was actually legal, but I did it anyway.) What was in it? A fried X79 mobo and 650W PSU... but what works perfectly is the: 32GB of RAM, Intel 10Gb NIC, 4930k CPU, and Quadro M5000 (the 8GB GM204 card). Obviously it's a dump after an insurance claim over a surge of some kind, all the drives were gone, including the cage. So I bought a new-ish Asus P9X79 off ebay (the board I tested everything on has 2 bad memory channels), dug out a spare 600W Seasonic PSU, and I'm going to put it back to work.
Moral: Don't be proud, dig through the trash and see what you can find.