I came across a cool web service called Tagcloud. The site creates a tag cloud of keywords based upon whatever RSS feeds you give it. I decided to create a Tag Cloud that included some Salesforce blogs: mine, Salesforcewatch.com, Successforce and the Sforce blog.
The permalink to the tag cloud is http://www.tagcloud.com/cloud/html/Salesforce/default/50
To change the number of tags displayed, just change the number at the end of the URL (currently 50 tags are shown).
Since most rss feeds do not contain a full history of posts, the cloud is only made up of the posts in the current feed.