These malls are FREE to join. They all offer some form of rebate
GSC Suggests you join each mall, this way you can comparison shop.

Mall 1  My Power Mall   

Offers cash rebates when shopping. Two kinds of malls, Personal and Business. You can start a home based business for free with the business mall. Rebate amount is determined by the type of mall and store.
Mall 2 Ebates  
We each get $5.00 when you buy your first item through the mall.
This is a cash rebates similar  to MyPowerMall. The rebate amounts are about the same. I prefer to use MyPowerMall, because part of the company's profit goes to help someone in need.  I usually try MyPowerMall first, the go to malls 3 & 4
Mall 3  My Points 
Get points when you shop.
Mall 4  Memo Link
Similar to MyPoints 
  
Coupon Malls