Hi Butt,
There's a huge range of choices out there, all depending on your budget, needs, time etc. As a hobby I've put together a number of PCs, and my suggesitons (and they're only that!) for consideration are based on my own current setup. It also depends somewhat on whether you're planning to DIY or go for a brand name. On that score, all I can say is avoid Compaq like the plague
(Apologies to satisfied Compaq owners.)
CPU - AMD, either Thunderbird or Duron. Durons are cheap, stable and if you're that way inclined, can be tweaked for more "oomph". Purists will argue that intel are "better", which they are on the whole, but there's not much between them. If money's no object, go for the fastest intel you can. Otherwise, stick with AMD for much less money.
Motherboard - Socket A (if using AMD CPU), with ATA100/RAID support. Abit KT7-Raid is a good one.
Hard-disk - IBM ATA100 are great, and combined with the RAID m'board, will enhance gaming performance. A pair will be even better (RAID works best using identical HDs). Twin DTLA307030s would be nice!
RAM - Minimum of 128MB, the more the merrier, but not "slower" than 133mhz. you might not notice the difference, but the hardware will. As with the HDs, using identical RAM types is better.
Video card - AGP. As a guideline, focus on the chipsets rather than the brand names, as many companies use the same. Nvidia GeForce2 does very well. I'm not an avid gamer, but a cheap and cheerful (Winfast) card does the job very well. N.B. Some motherboards will have graphics "onboard" but if you're wanting more gaming power/performance, steer clear.
Sound card - Depends on your speaker setup and the room you're in, but a Sounblaster Live! value does very well. If you're into playing DVD/MP3 etc and want hifi type performance, maybe a higher level SB card would be better. Same N.B. about onboard sound as with graphics.
CD/DVD - According to your needs. I use a Pioneer 115S DVD, which is fine for all uses. Only rarely play DVDs though, so it's primary use is as a CD-ROM. Watch out for regional coding issues with DVD if you go that way. Panasonic drives can be set to read all regions, whereas Pioneer will be fixed on/after the 5th change of region.
Floppy - All pretty much the same.
Power supply - Important is you're going with an AMD system, as they are more greedy than Intel. Not less than 300W should be plenty. If you have lots of USB hardware without its own power supply, consider something more wattage.
Bear in mind whatever you go for will be outdated in a few months, so don't go for the very latest stuff, as it will cost you. That's why I lean towards AMD now. A US$60 AMD CPU giving similar performance to an Intel one, but at 25% of the price speaks for itself.
Take time to look for reviews which will give you a good idea for a shortlist. Good hunting!