In a short period of six months, RetailMeNot has grown into one of the most popular coupon sites on the Internet. They even have a handy Firefox extension you can use to save money when you're just about to pay full price online by alerting you to an applicable coupon code: RetailMeNot Firefox Extension

There are some coupon codes available for vault.com, a website specializing in career and education information. You can save at popular stores such as Gap, Circuit City, Barnes and Noble, Blockbuster, and other services such as Netflix. The nice thing about each coupon code offering is that there are user comments posted that help you understand exactly what you're saving and how.

If you sign up for the "Hot coupons" Newsletter, they'll deliver the latest and highest rated coupons directly to your email inbox every week. You can sign up for all the stores or just alerts for single shops.