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.
Direction Local - Quickly Boost Your Local Search Rankings
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Clearscope - Data-driven content performance optimization platform
Site Search 360 - Site Search 360 enhances and improves your built-in CMS or product search with autocompletion, semantic search, filters, facets, detailed analytics, and a whole lot of customization options.
WordLift - WordLift is an artificial intelligence-based search engine optimization tool that helps you to attract more traffic to your website and generate a large amount of revenue.