Wordle.net.
Wordle is a site that generates word clouds (similar to the tag clouds) off
any text, RSS feed, del.icio.us tag or URL you provide. The clouds give greater prominence to words that appear more frequently in the source text.
You can tweak your clouds with different fonts, layouts, and color schemes. The images you create with Wordle are yours to use however you like. You can print them out, or save them to the Wordle gallery to share with your friends.