Altosight - eCommerce price monitoring & tracking software
Honey - Honey is a browser extension that automatically finds and applies coupon codes at checkout with a single click.
Bidvoy - Bidvoy is an effective product value tracking service for eBay that is providing complete requirements as far as auctions are concerned.
Price Snoop - When viewing a product on Amazon, Price Snoop will show you just how much it costs on the other...
Auction Price Finder - Check the current value of any item on ebay, based on the last sales.
Slickdeals.net - Slickdeals: The Best Deals, Coupons & Discounts on everything