RetailMenot - The RetailMeNot mobile app allows you to find deals on the go for both online shopping and in store shopping.
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
Slickdeals.net - Slickdeals: The Best Deals, Coupons & Discounts on everything
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Honey - Honey is a browser extension that automatically finds and applies coupon codes at checkout with a single click.
Klevu - Klevu offers instant site search solution for eCommerce stores.