'cash back' sites-- any recommendations?

I've seen various cash-back sites mentioned for years, but have never used them. I'm wondering if anyone who has used them might have recommendations as to which might be the most reliable for giving credit?

I've seen ebates (of course), TopCashBack, and BeFrugal-- I imagine there are others I'm not aware of.

ebates and befrugal work well. Not used topcashback