Ok so I posted the Target deal that got better by using Ebates yesterday, but wanted to give you a formal introduction to Cash back offers.
There are actually a number of companies that allow you to get cash back when you go through their sites to make online purchases. I have had experience with the three main ones: mypoints, shopathome, and Ebates.
While I got some great gift card rewards from mypoints when they were doing a sort of rare special offer, I don't like the "point" set up of their site and don't think that their offers are as good as the other two.
I have only used shopathome once, but was able to get a travel coffee cup that was originally $10 for the equivalent of $2 as one of their "daily deal" type items, where they have free shipping, an increased cash back rate and a special sale.
Ebates has been easy to use, pays via check or paypal, and has helped me to make some great deals even better. While they only have 4 payout sessions a year, they do it without you telling them to unlike other sites, and will send you an email if you haven't set up everything correctly.
From now on we will try to post when we think a deal would make an especially good matchup for any of these cash back programs. Your best bet though is to sign up for them now and then bookmark them or do something to help you to remember to go through them for your future online purchases :)