There are actually websites that pay you cash for shopping at certain stores!  These sites are known as Cash Back Websites or Online Rebating.  Each site gets a commission for referring a customer to a site.  They in turn pass that cash onto you!  Each site offers links to thousands of stores at a varying percentage cash back.  The amount does change frequently, so check back regularly to see

Using them is simple- simply register for a free account.  Instead of visiting a store’s website directly, log into your cash back account and select the retailer from their list.  You will be taken directly to the retailer’s website, but a percentage of your purchase will be deposited back into your account.  You will receive a payout each quarter.

Ebates

Upromise