I recently came across an interesting website called Retail Me Not. The premise of this site is simple: Gather a bunch of reusable discount coupons for online stores and post them for everyone to use. The site uses a simple easy-to-use search interface to find discount coupons for your favorite online shops.
Users can click a yes or no button to let others know if the coupon worked or not. Stats display the percentage of how often the coupon works. You can also submit discount coupons that you know of and share them immediately with other users.
Visit the site at: http://www.retailmenot.com/