Honey - Honey is a browser extension that automatically finds and applies coupon codes at checkout with a single click.
Groupon - Each day Groupon offers a deal through local vendors in your city.
Invisible Hand - InvisibleHand gets you the lowest price on shopping and flights.
RetailMenot - The RetailMeNot mobile app allows you to find deals on the go for both online shopping and in store shopping.
Offers.com - Offers.
Capital One Shopping - Get the best coupon code, the best price, and alerts when items you viewed go on sale.