Check out BlogScope's tools for visualizing content from over 30 million blogs and 520 million posts. The site (http://www.blogscope.net/) currently is in preview/beta release, but has some nice tools allowing you to track the popularity of a search term, as well as running a comparison against two search terms (see below for an example). BlogScope also allows the embedding of their charts in other content ... such as blogs.

Overall, this is a good tool, it will be interesting to see if they develop additional analysis modules, as they could begin competing against some of the larger buzz monitoring outfits.