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.
Meta Search - Search your Desktop, Google Drive, Dropbox, Gmail, Evernote.
Sumo - Free tools to grow your email list.
List.js - Tiny, invisible and simple, yet powerful and incredibly fast vanilla JavaScript that adds search...
Swiftype Site Search - Swiftype Site Search helps to sell more, get the right answer to more people on the platform and surface relevant content for readers and followers.
xendo - Fast search for all your work. See all your important documents, emails, contacts and updates with one search.