The first purchase, the case. Aside from the motherboard, one of the more importat parts of the machine, in my humble opinion. Sure, you can build a computer sans a case, but then the cats attack your video card, and chew on the power cables inside, rather than outside.
So, to kick off the running commentary of my adventures of computer building, here's my case. The Supermicro SC760P4 with 300w power supply. Those of you who've knownme for awhile will remember me drooling over the SC750. This is pretty much the same thing, but some slight design changes, and I *think* better cooling? Not sure, but hey. Price: $151.51
And awaaaaay we go.