Product Category Dropdowns
Displays product categories as dependent drop-down selects.
Plugin tag: search by category
Category Wise Search
Category Wise Search Widget plugin.You have option search specific category content.
Swiftype Site Search Plugin for WordPress
Fast, intelligent, and fully customizable search for your site.
Advance Ajax Live Search
Search By Author-Tag-Cats-Date And Keyword.
Keyspider Site Search Plugin for WordPress
Relevant, intelligent, and fully customizable site search for your WordPress website.