From now through Oct. 29 you'll receive $10 of in-store credit for every $50 you spend on U.S. PlayStation Network. The deal, which goes for up to $100 worth of credit, applies to any Sony Entertainment Network purchases, but we know where we'd spend it.
If you're wary of digitally pre-ordering cross-gen releases, keep in mind you can upgrade to the PS4 versions of Assassin's Creed 4: Black Flag, Battlefield 4, Call of Duty: Ghosts, and Watch Dogs for $10 each. That means your initial PS3 purchase will net you enough credit to cover the upgrade fee once it's time to switch to PS4.
You could also pick up or renew a one-year PlayStation Plus subscription for $50. Whichever way you do it, the SEN credit will be dispensed to your account by Nov. 8.
Sony also has a suite of exclusive themes and other rewards set up for PSN pre-orderers, which you can check out on the PlayStation Blog.