Core2Duo processors are the current king of performance. Unless you want to drop some money on a quad core.
I went with
this motherboard from Asus. There's quite a few out there, though. One of the actual Intel-based boards are pretty solid too. I almost went with the
DS3 board from Gigabyte.
As far as video card... just depends on how much you want to spend. I went with a 7900 GS just because I don't game much.