Get an i815E or EP based board. The Asus CUSL2 (E) or CUSL2-C (EP) boards have the best reputation among all 815's.
Why? Because Asus is known to make the best mobo's in the world. For stablity, speed, overclockabilty, BIOS upgrades and extra features, these boards are simply the best. The -C is about $ 25 cheaper than the CUSL2, because it does not have integrated video (i752) and has 4 USB ports instead of 7, etc. Yhey can be bought on the net for about $ 100.