I second everything that 11H1P said, to a 'T'.
My personal preference is Abit motherboards. They got some pretty cool stuff, and their boards are high quality. But Asus and Tyan are good too.
I like to get my memory from [url]www.crucial.com[/url]. In my personal opinion, it's the best memory, period.
I would suggest going with a Western Digital, IBM, or a Quantum hard drive. In my sort-of professional experience, Maxtor and Seagate blow big chunky gooey dripping chunks. Unless they got better in the last 5-6 years, and I haven't heard anything.
Make sure the motherboard's BIOS supports the size of the hard drive you get. I've been out of the loop for a while, but there's some hard drive size limitations regarding BIOS. Just check to be sure.
For some brands of motherboards, you can go to [url]www.motherboards.com[/url]. I'm not saying to buy from them - I'm just saying you can go there. They list more specs than you actually need to know (at least, for the ones they sell, anyway - Abit, Gigabyte, Soyo, Transcend, Iwill, and Epox). I find it a good reference site when looking at new boards. Unfortunately they don't seem to have Asus or Tyan.
And, for the "phony-tough and crazy-brave", if you want to see some damn good deals (but no guarantee you're buying from a reputable source), try [url]www.pricewatch.com[/url]. It's basically a place where different stores can put up their cheapest prices, and they get listed in ascending order, cheapest price first. But be careful. What I like to do is look for the cheapest price that is also from a name I've heard of, or am familiar with.
Soon, I'll have to build a new system to replace this aging celery 400 I built 4 years ago. But it's still fast enough to play Deus Ex, Thief 2, and Unreal Tournament, as well as the original Zork, and Angband, so I'll be fine for a little bit longer.