Money Saving Resources has a variety of useful online coupons. You can search by store or just check back often since its updated daily. There are also forums where people share various coupon codes.

Everyone knows Wikipedia. Well this is Wikipedia's coupon page, which has a lot of great information and even better it has a lot of great links.

Wow Coupons is another site that offers a variety of coupons. Not only do they have online coupons but they have printable coupons for brick and mortar stores. They have an astounding collection of coupons for nearly all of the most popular brands.

Coupon Cabin has been around for years. They update their site daily with online coupons for the most popular stores. You can view by most used coupons, compare prices, favorite deals, or check out their money saving forum. They also offer a printable coupon section.