Grocery Smarts. This website takes the advertised sales of stores, and compares them to coupons, both online and in the circulars found in Sunday newspapers. So, even if you don't get the newspaper, you can still do a lot of couponing, and save a lot of money. All you need is the Internet, and a printer.
Another thing that I like about Grocery Smarts, is that it rates each item, using stars, telling you know how good of a sale it is. You can find stores in your state by clicking on your state in the drop down menu on the top left side of the main screen. There is a tutorial on how to use the site here.
Coupon Mom offers a similar service. It has some features, like sorting, that I really like.