Sooqr - Sooqr Search provides relevant and innovative site search engine for the website.
Zoom Search Engine - Add search to your website, Optical Character Recognition* (OCR) for images and PDF, Huge indexing optimizations Multi-threaded Offline Indexing
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.
A1 Website Search Engine - Create search engines for online and offline website content.
Klevu - Klevu offers instant site search solution for eCommerce stores.
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.