My vote is for the IWill KK266. Hits extreme fsb speeds consistantly, very affordable, and is making the review rounds and doing extremely well.
Check out some reviews and shootouts, and it's always good to check message boards and see what problems people are having, etc.
KT7a is very nice, but with all the stellar reviews of the KK266, I decided to check one out for myself. Picked up the RAID version at a computer show 10 days ago for about ~$145, and never looked back. Running great with my tbird clocked >1.5ghz, no BSODS, and it's been crunching RC5 24/7 (100% CPU utilization) since I installed it. Very nice board, and the price is awesome.