When shopping online, in addition to earning cash back from your credit card, there are many cash back reward sites that also give you an additional cash back if you shop via their referral link. Essentially, if you follow their link the site gets an affiliate referral commission from the store for your purchase that they share with you. The cashback varies store to store and often ranges between 1% to 5%+.
I am registered for a number of such cash back sites (ebates.com and simplybestcoupons.com are my favorite). Since each rebate site offers a different commission, a good way to be sure you are getting a maximum cash back there is cashbackholic.com.
There I enter a store name where I plan to buy from, and it lists all of the cashback sites for that store sorted by highest cash back percentage.
I check which of the cash back sites I normally use offer highest commission, and click through that link.
So an extra minute before I place an order saves me an average of 3% on all of my online shopping.