I know that data visualization can be a very high-tech exercise that requires programming knowledge, but I would like to draw attention to some free low-tech word cloud generators.
I find that the web-based tools like the ones below can be great for presentations and for teaching, and can really foster discussion when courses or presentations are conducted online.
5 free word cloud generators:
Wordle — A text "toy" -- input text right into a text box or have the toy scan a URL. It is a Java Applet so would require a screenshot to make a JPG or PNG image.
Jason Davies's Word Cloud Generator — This is also a simple toy that will let you type or paste text or alternatively provide a URL. There are different options for marking word prominence, as well as how to display the cloud. You can generate a PNG with this that will open in a new window or tab.
Tagxedo — This is a URL and search-based tool, so you can plug in a URL or a news item, for example. If you use Twitter often in your classroom, you can visualize a Twitter handle's entire output, or a blog's RSS feed. It also has more options for fun shapes, as in this visualization of my blog as a star, below.
WordSift — Developed by Stanford University, this tool accepts typed or pasted text. Upon generating the simple word cloud, it provides a thesaurus mapping of the prominent word and points to the use of that word within the text. It also allows the user to click on other words in the cloud to in turn generate their respective map and usage. This was created with English language learners in mind and may be useful to classrooms with students working with English as a foreign language.
Tagul — This site requires a free sign-up and has more options for designing word clouds (it is also linked up to Zazzle to custom print your word cloud on various items). The ability to customize your shape is a nice feature, which you can achieve by uploading an image of the shape you want.