Buy.com has a new coupon for
$5 off $50 [Exp 3/31] for new customers. Other new customer coupons include:
$10 off $150 and
$15 off $200 (these two have no expiration date). They also participate in Google Checkout's $10 off $10 purchase for new customers to Google Checkout (not stackable with Buy.com coupons above).