This great free tool is amazing. Copy any text or complete website from the internet. Paste it into the wordle.net box on their page, click create and you get a tag cloud where the most frequently used words from your text will be shown as large words whereas the lesser used words will be very small. I reckon a great way to collect e.g. group findings, opinions in class or to introduce a new topic.
Here is a wordle made from the BAG Homepage:
