I really like AnswerGarden. It can be used for brainstorming, polls, comments, or answering questions. You don't have to log into or register for AnswerGarden, so elementary students can safely use it.
Click "Create an AnswerGarden" and type in your question. You can click on more options to password protect your AnswerGarden if you want to go back and edit the question. After creating the AnswerGarden, it can be embedded into your blog or wiki, or can be shared as a link.
A word cloud is generated from the answers. Below is a sample AnswerGarden embedded into my wiki. Please submit an answer to see the garden grow!
What would you use AnswerGarden for?... at AnswerGarden.ch.