I'd like to propose the integration into the WordPress core of including search URIs in the permalink options. By default, when a user performs a search, they are directed to a results page at /?s=search+term.
Instead, I would like to see -- and hopefully others would, too -- the inclusion of a simple RewriteRule to change /?s=search+term to /search/search+term.
Mark Jaquith's simple Nice Search plugin performs this function very well. I include it in every new install of WordPress.