ABCya Word Clouds is a site that allows you to create word clouds from any text that you copy and paste or just type into the site. This is similar to http://www.blogger.com/www.wordle.net except that ABCya allows you to save the image it creates as a jpeg. You can do the same with Wordle but there are a few extra steps involved. ABCya is customizable so that you can choose your colors or the style you want. Give it a try. Here's a word cloud created from my blog posts.
Here is a list of other word cloud generator sites:
Big thank you to The Whiteboard Blog for the list of word cloud generators.