TagCloud searches any number of RSS feeds you specify, extracts keywords from the content and lists them according to prevalence within the RSS feeds. Clicking on the tag's link will display a list of all the article abstracts associated with that keyword.
The tagcloud to the left includes the feed to my site and to blogcritics.org
One can add multiple feeds to the same cloud, occasionally with wierd results.
Now if only I could figure out how to plug my del.icio.us feed into blogger