If you like using Wordle; another website that allows you to make word clouds is Word It Out.

Simply enter some text and create your word cloud. You can then share your cloud if you want to. It is also possible to embed it on your blog or website.

Note that just as you can with Wordle you can use the tilde (~) character to keep words together.
A great feature for mathematicians – WordItOut can easily cope with the equals sign, division signs also – see for example this equation.  (It is possible to use the equals sign in Wordle – use Advanced).
It seems other symbols are possible also.

Various options are available, you can change the colours of your words and the background colour, you can also change the size of the font and the variation in size allowed.

Emma made our Year 7 class a poster of the vocabulary needed for our work on shapes and here is a very simple example on Linear Sequences.