Never search for a coupon again! Coupons at Checkout uncovers coupon codes automatically at thousands of online stores. Wherever you see a ‘Coupon Code’ box, now just click to see all the retailer’s latest coupons!
Here is a little more about this add-on from the developers:
The Coupons at Checkout (TM) Firefox extension saves you money at thousands of ecommerce stores, automatically. Wherever you see a ‘Coupon Code’ box on a retailer’s checkout page, Coupons At Checkout will find all the latest coupons for you. Just click on the box to see them, and select a code to apply it to your order.
Want to learn more? You can grab Coupons at Checkout from the Firefox Add-ons website.