CNet notes a drop in prices for AMD processors:
Sunnyvale, Calif.-based AMD lopped as much as 31 percent off its list prices for Athlon XP-M processors and reduced prices on a handful of Opteron server chips by as much as 35 percent.
According to Pricewatch, it looks like the sweet spot in Athlon XP processors is on the 333FSB Athlon XP 2600 (currently at about $97 + shipping).
Now where is my Athlon64?
Update: Kenneth definately has the right idea: go with the Barton core 2500+.