I'm sure a lot of you out there reading this are already members of Mr. Rebates or Ebates. For those of you that aren't, you have to join TODAY!! First of all, you'll get a $5 bonus just for signing up at Mr. Rebates and Ebates.
In addition, check out these cash back sites: FatWallet and BigCrumbs
Then, every time you shop online, go to one of these websites first to see if they offer cash back when you click through them. I always check all of these sites to see who offers cash back and at what percentage.
After you reach a certain amount in your account, the sites will issue you a check or pay you via Paypal! It's really that easy to make extra money for doing what you already are doing--shopping online!
Don't forget to also check out coupon codes (note that sometimes using a coupon code not found on a cash back site will negate your cash back, so be careful!) on RetailMeNot.