This one I came to me from Ana Falcon by email on the ELTECS-Latinamerica list…Wordle allows you to take a text and turn it into a word cloud and then to customise it in a variety of cool ways. My original text was about El Alux, a spectacular bar located underground in a cenote, a geological formation in the Yucatan.
What could you do with Wordle with learners? In her message, Ana suggested "You can print them out, or save them to the Wordle gallery to share with your friends". My suggestion would be that it's another example of something you shouldn't be doing — but that your learners might enjoy, especially if they are young.
Would they actually learn anything from it…? I'm not entirely convinced that they would. But they would have fun doing it, and it would involved actively doing something; it could be a way of persuading them to look back at previous texts (or finding new ones); it might be a way of revising vocabulary if what you asked them to do was turn a text they had "done" into a Wordle; and if you had a class blog it would produce some attractive images (you would have to take a screen capture and edit it [how?], as it's not possible to create an image directly at Wordle).
The ELTECS lists are well worth subscribing to — apart from anything else for the links Ana suggests at regular intervals.