I went and had a little fun with wordle this morning, these two word clouds are McCain's vs. Obama's acceptance speach. It is a pretty cool little web application, I'm sure you could make some pretty nice posters using these word clouds as a base.
"Wordle is a toy for generating “word clouds” from text that 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 friend"