Before you shop online, take a look at
RatherBeShopping. This site lets you search by category or retailer and find active coupons that you can use on checkout. Click on the coupon and you'll be redirected to the retailer's site where you can enter the coupon code and get your discount.
There is no shortage of retailers, including major ones like Amazon, Expedia, Zappos, Best Buy and Stub Hub.