The Champions Online Website has a post outlining preorder bonuses for Champions Online at GameStop, Wal-Mart, Best Buy, and Amazon (thanks Massively). The update also outlines plans for beta testing on August 17:

Atari and Cryptic are proud to announce the official Preorder promotions from retailers across the United States. In addition to specific exclusive promotions for each retailer, all preorders (from any retailer) will receive guaranteed access to the Champions Online open beta, beginning August 17th. All purchases also include 30-days of free play and five Cryptic Points to be spent in-game.