Douglas Brown has put together an announcement for a web service he's come up with (and made available for download) to make a tag cloud out of the top keywords from your twitter feed.

The problem I was having was actually judging whether or not it would be worth my time following their tweets. I mean, I follow someone that is really respected in a certain field, only to find out that they tweet about their new puppy they just got more than anything. So I made a PHP script that generates a "Twitter Tag Cloud." Using this, you can generate your own Twitter tag cloud to put on your personal site to display the top keywords that you have been tweeting about.

You can either check out an example of the cloud through the form in the post, use his REST service to get the keywords for a user or you can download his code and try it out for yourself.