Any motherboard that supports the XP processor and 333MHz FSB should work for you. You didn't say what your priorities are (the best regardless of cost or sumptin cheap) so,,,no suggestions. But I do have a link (just look for XP and 333):
http://www.newegg.com/app/ViewProduct.asp?submit=property&DEPA=1
Hope this helps! 
One thing to keep in mind is the VIA chipsets after KT266A (which is slower than you want) refer to memory speed, not FSB speed.
For example, the KT333 chipset may or may not support FSB333, most Shuttle and Gigabyte KT333 boards do, most Biostar KT333 boards don't. KT400 boards support DDR400 memory, but not 400FSB officially, KT600 boards support 400 FSB, etc.
BTW, since someone mentioned
www.newegg.com, the reason I know all this is b/c I recently purchased a refurbished Shuttle KT333 mobo for $23 with shipping from newegg, and I am very pleased with it. You only get a 15-day warranty on refurbs, but for 1/3 of the price, it's hard to beat.