I ran into a site that is a lot of fun to play with. Wordle is a small java applet which will build one of those word clouds based on text you enter, or given a URL it will build the cloud based on the page. You can check out my cloud here
They also give you html you can use to link the image right into your blog. Which I have done with this post:
If you've had success with this service, or know of any other like it leave a comment. Thanks!