Most bikes are designed to handle 220 pounds, which means they can handle more but become less reliable as the weight goes up. Don't get fancy racing rims a lot of these guys mentioned, like the Bontrager Race or the Mavic Ksyrium Equipes or low spoke count wheels; these wheels are for the deep pocket people who don't care about durability more then they care about the weight or looking cool. Go with a simple box rim like the Mavic Open Pros, Ambrosio Excellence, or the Torelli Master Series, or Sun M15's, these rims all come in a 36 hole configuration and all have double eyelets for more strength.
Read this for more info on the subject of wheels because I'm sure I started a small war:
http://www.roadbikerider.com/UArant2...sible%20Wheels