Someone asked earlier re alternatives to the (pretty much) standard "All in One" SEO plugin for WP. Here's a good one
* Automatic 301 redirects for any permalink changes
* Optimized Post and Page Titles for search engines
* Generates all SEO relevant META tags automatically
* Helps you avoid duplicate content
* Lets you override any title and set any META description and META keywords, for any post or page
* Compatible with most other plugins, like Auto Meta, Ultimate Tag Warrior and others.However you may have to disable All in One SEO pack
* You don?t have to fear changing permalinks. If you are not satisfied with the current permalink, change it through Settings>Permalinks in your admin panel, without worrying about loss of Page rank or google penalty.Platinum SEO plugin will take care of issuing a 301 redirect to the new location.This is a new essential feature, not present in All in one SEO
* Add index, noindex, follow or nofollow, noodp, noydir, noarchive, nosnippet meta tags to any post/page.These options are not available in All in one SEO Pack.Find out why this option to set post/page level Meta Robots Tag useful?
http://wordpress.org/extend/plugins/platinum-seo-pack/