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.
Hawk Search - Site-search engine for eCommerce platforms.
Dynamic Yield - Personalization & customer experience management
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
Optimizely - A/B testing you'll actually use.
Swiftype - The simplest way to add search to your website or application. Sign up for free.