ykjsw

wpReplacer is a post rewrite plugin, it can automatic rewrite your posts or pages
you can setting:
Replace Level: Good replace the most terms Better fewer replacements, higher quality Best fewest replacements, higher quality
the percentage of replaceable words you would like to rewrite
Negative Words: words that will not be replaced

WP Replacer

wpReplacer is a post rewrite plugin, it can automatic rewrite your posts or pages

craigsimps

This is a super-simple plugin which will turn WordPress’ default <code>/?s=query%20terms</code> into <code>/search/query+terms/</code> if you have pretty permalinks enabled.
This is something which I have been placing into a theme include or in a core functionality plugin until recently, but it makes sense to separate this functionality out into an individual plugin so it can be switched on and off independently.
The plugin has no administrative interface or control panel. Activation turns it on, deactivation turns it off. Once activated, performing a search using the standard WP search widget should give you a much nicer search URL.

Simple Search Rewrite

Redirects search results from /?s=query to /search/query/, and converts %20 to +.

WP Replacer vs Simple Search Rewrite