http://www.relevanssi.com/

Search results sorted in the order of relevance, not by date.Fuzzy matching: match partial words, if complete words don't match.Find documents matching either just one search term (OR query) or require all words to appear (AND query).Search for phrases with quotes, for example "search phrase".Create custom excerpts that show where the hit was made, with the search terms highlighted.Highlight search terms in the documents when user clicks through search results.Search comments, tags, categories and custom fields.Adjust the weighting for titles, tags and comments.Log queries, show most popular queries and recent queries with no hits.Restrict searches to categories and tags using a hidden variable or plugin settings.Index custom post types and custom taxonomies.Index the contents of shortcodes.Google-style "Did you mean?" suggestions based on successful user searches.Automatic support for [WPML multi-language plugin].Automatic support for various membership plugins.Advanced filtering to help hacking the search results the way you want.Search result throttling to improve performance on large databases.Disable indexing of post content and post titles with a simple filter hook.Multisite support.PDF content indexing.Search result throttling to improve performance on large databases.Improved spelling correction in "Did you mean?" suggestions.Searching over multiple subsites in one multisite installation.Indexing and searching user profiles.Weights for post types, including custom post types.Limit searches with custom fields.Index internal links for the target document (sort of what Google does).Search using multiple taxonomies at the same time.

Changelog

* Security fix: Prevent CSV injection attack in log export.

* Security fix: Restrict access to doc count updates.

* Minor fix: Product variations check the parent product for access restrictions, to avoid situations where variations of a draft product appear in the results.

* Minor fix: Improved TablePress compatibility.

* Minor fix: Added error handling to the Ninja Table compatibility code.