For many years, I have been using the site Mypoints, a loyalty program of a different kind. This program gives you points for shopping, surveys, or clicking on the link in targeted advertising. Points can then be cashed out for a gift card from a number of stores (I just cashed out for a $100 Macy's gift card.). While the shopping rates aren't quite as good as many of the shopping sites, they do offer frequent bonuses.
I have the best luck clicking on the link in the targeted ads they send me. The email will tell you how many points (usually five), if any, you get for clicking on the link. I only click on the ones that give points. Often, you will get bonus points for filling out a form, signing up for a free program, etc. Points are worth just under a penny per.
You won't get rich quick from the site; For that matter, you won't get rich slowly. But $100 gift cards once or twice a year are kind of nice.
Oh, and since I'm sure somebody will ask, I do not receive anything if you sign up.