If you want to assess how well you're targetting a particular keyword with your on-page SEO, http://www.seomoz.org/term-target is a great tool for telling you just that. It analyses the positioning of the keyword in all on-page areas and throws in a few other factors too. I've found this very useful in the design process of a few web sites recently and thought I'd share it for anyone else who doesn't already know about it.