I've created a new wordpress plugin called Clean Trunks to help automatically seo post slugs in a smart way. The plugin truncates the post slug to a configurable length and filters the page name against a stopword list to strip out useless keywords. The result should be short and sweet keyworded urls!
Includes an admin screen and is under GPL.
I was looking for a solution like this, and apparently not the only one: http://wordpress.org/support/topic/44342