Below are links to various cash-back sites.  Use Cash Back Monitor to compare rates at each store.

Rakuten 

Top Cash Back 

Ibotta (Save on in-store and online grocery purchases)

Mr. Rebates 

Swagbucks 

BeFrugal 

Simply Best Coupons 

Rebates Me 

Max Rebates 

Active Junky 

ExtraBux