I know everyone is probably going to stand beside the motherboard they purchased whether it is the most stable or not... but aside from all the stories about the abit KT7-RAID mine has been rock solid.
It handles my 900 t-bird to easily do around 1.05 - 1.1 GHz and stable as can be in win2k. Hell, I didn't even realize it, but for a while my northbridge fan had stopped spinning and it didn't even affect the performance.
But, I would have to second the other two choices, from my experience those are also excellent boards.