http://www.goodsearch.com/goodshop.aspx

I like to use "GoodShop."
Download it and whenever you go to a shopping site in its network it notifies you of any coupons they are currently running. It shows up on their toolbar if you choose that option.
They also notify you if the store will make a donation to your choice of charity organization.
I also use the "GoodSearch" search engine b/c they make donations when you search as well.
It is not the best, so I switch when I need something more high-powered, but it is an easy way to support your favorite charity!

Have fun shopping!