Ebates is advertising December "Double" cash back for the holiday shopping season. Oddly the 'double' doesn't seem to be literal since they are advertising before rate of 3% and after rate of 5% for some merchants.
Here is a list of some of the featured rebate deals on Ebates:
Sears has 4% back
HP's store is 5%
Old Navy is 10%
Target is 5%
Barnes & Noble at 8%
Kohl's at 4%
These are just a few of the stores that you can get rebates for from Ebates. If you're doing any online shopping then I'd recommend checking out Ebates to see if the merchant has a rebate there.