In the U.S., I'd check out these:
http://www.bhphotovideo.com
http://www.adorama.com
http://www.buydig.com (a.k.a., beachcamera.com)
http://www.amazon.com (making sure to buy directly from amazon.com versus one of the merchants listing gear there, so that you get amazon's better return policy; and to make sure you're getting a camera intended for sale in the U.S. for warranty purposes, as vendors with cheaper prices are often selling gray market gear).