POTENTIALLY VERY HOT: From August 1 until September 30, 2009, you’ll earn 5% cash back on eligible back to school purchases with your PenFed VISA Platinum Cash Rewards credit card. Eligible purchases include computers, computer peripherals, software, consumer electronics, office supplies and books.

I could not find mention of a cap on rebates for this promotion, which would make it very hot when you actually take a look at the list of retailers which are eligible. Every major electronics store, computer manufacturer and book store is listed, including Apple, Dell, HP, Amazon.com, Best Buy, among a host of others. More info and the list of eligible merchant category codes can be found here.