I've just recently become aware of these. Say you need to go to Wal-mart.com, so instead of just going there, you go in through a shopping portal. Maybe for Wal-mart you will earn 2% cash back on your purchase. I have run on several of these and have used a couple of them. E-Bates, Chase Ultimate Rewards, MyPoints, Inbox Dollars. Then if you purchase your items with a cash back rewards card, you can earn even more. The hardest part is remembering to use it. They can be used at many, many different stores. For some reason I can remember to use it at Walmart.com, but I can't remember to use it at Amazon!
I have seen the commercials that advertise cash back portals. I have never known of anyone who used them though. Keep us posted and let us know if it is worth using them. Thanks.
I'm in the UK and use a site called Topcashback. Besides cashback, there are daily clicks and regular competitions. Whilst it can take some time for the cashback to appear in your account, they do pay you very quickly once your money clears. Some of these websites have a browser extension, which will alert you to any cashback which is available on the website you are visiting.
I have used the shopping portal twice so far, and it did pay very quickly. I got 2% extra cash back on purchases at Walmart.com and HomeDepot.com. Then I paid with my rewards credit card and got another 1.5% cash back. Pretty cool deal!!