I do my online shopping via Ebates, where they give a cash rebate for online purchases.
http://www.ebates.com/rf.do?referrerid=L0xgq26veNU%2Ft6Qqy6ndDQ%3D%3D
Many major online merchants give rebates (including hotels and car rentals), usually 2-5%. It adds up in the end.
Some places give a rebate if you order online and pick up in store (BBB, Home Depot, Nordstrom).