WordPress SEO by joostdevalk is a complete SEO plugin that exists today for WordPress.org users. It incorporates everything from a snippet preview that helps you optimize your page titles, meta descriptions and keywords to XML sitemaps, and loads of optimization options in between.
Post titles and meta descriptions
Robots Meta configuration
Permalink clean up
Edit your robots.txt and .htaccess
Clean up head section
Download and info: http://wordpress.org/extend/plugins/wordpress-seo/