Ebates is a great site that gives you cash back for shopping you already do on the internet!
I found a great post explaining all about ebates on Doughroller.net
If you are a new member you will get a $5 bonus on top of the cash back!
Sign up here!
Each purchase you make, check ebates first, login to ebates and find the site through their search. This will track your purchase and you will receive cash back to your ebates account. I believe they pay out every 3 months.
I received a check for $8.54 in October, and now between holiday shopping and a new laptop purchase, I've accumulated 49.85 for my next check.