Tricider lets you write a question (without registration) and then anyone can propose an answer with supporting reasons. People can then vote on which answers they like best. Responses are not moderated, but it appears that the originator can delete them.

You can see an example that Nik Peachey created: How do we encourage pedagogically sound exploitation of technology in language learning?

I’m adding it to The Best Places Where Students Can Create Online Learning/Teaching Objects For An “Authentic Audience.”