An Advanced Search plugin
This advance search plugin allows user to input search options.
Site map to help visitors navigate around your blog.
PhPExec
Execute dynamic php code in post.
Search reloaded plugin
The search reloaded plugin for WordPress is an enhanced search engine for WordPress.
Search Meter
Keeps track of what your visitors are searching for. After you have activated this plugin, you can check the Search Meter Statistics page to see what your visitors are searching for on your blog.
Search and Replace
This is a plugin for Wordpress to allow you to search and replace text across all your posts.