Guys a few corrections:
The Abit KR7A-133 that andy originally posted does NOT use the KT133 chipset. Yes that chipset is very old, but that board doesn't use it. It has the KT266A and actually its the fastest KT266A board on the market. The only thing newer is a KT333 chipset (both are made by Via) but honestly the KT333 isn't really much faster. The difference is in the memory it can handle, which IS faster (although not by much):
KT133 - SDRAM only (no DDR) PC100 or 133
KT266A - DDR SDRAM PC2100
KT333 - DDR SDRAM PC2700
So make sure you get the correct memory, but if you're not building it yourself you shouldn't have to worry. Incidently there is also a KT266 (no A) but it sucks and its hard to find anyway. Its slower and probably no cheaper than the KT266A. With Via, "A" means better. I just mention it just in case.
I agree, get an Athlon XP, not a Tbird. The XP 1800 is currently the best price/performance ratio.
Also, I don't see any brands listed, so just in case, this warning to you: Do NOT BUY GENERIC MEMORY!!! You will regret it. Go with a brand name like Crucial or Corsair. Kingston and Samsung are ok too, but Crucial and Corsair are the best. Just don't buy no name!