I've long wondered if it makes more sense to build your own desktops or buy them from an OEM. Both approaches have their merits, but for Linux shops, a lot of money really can be saved by rolling your own. As many readers pointed out, I could have gone really cheap on the machine my computer club and I built for our recent Linux Night giveaway. This especially makes sense for low-power applications, Internet access machines, thin clients, etc.
TigerDirect is always a good source for deals and bundles (case, power supply, motherboard), as is NewEgg. However, having largely been an OEM guy up until now, I completely forgot to purchase a CPU fan. Obviously, I'm well aware that I need one of these, but it's easy to miss important components when you buy a bundle.
What this points to, in fact, is the need to treat a roll-your-own project just like any other IT initiative. We're giving thought to rolling out simple workstations in several elementary settings where only Internet access is needed. The deals on TigerDirect occasionally look too good to be true, but a simple, comprehensive materials list for each machine can keep a project from being derailed by a simple oversight.
We almost weren't able to give away the computer we built for Linux Night since the local Radio Shack and the local computer repair shops didn't have any CPU fans compatible with socket AM2. I finally found one that would do the trick at another hole in the wall shop, although the apparatus I rigged up to secure the fan was pretty ugly (fortunately, a student won the computer, so she didn't mind waiting for a compatible fan to come in this week that could be snapped into place).
Clearly, the Linux Night project was thrown together and ultimately came together just fine. However, if building more than a one-off computer from scratch is in your future, all the usual IT skills apply.