Yack Pack

This seems to have potential, especially for those setting up Wikis or Blogs, though as it's online it can be used by anyone.

YackPack

Hard to explain but basically so watch this Video to see it in action

Basically as you can have all your students logged on and talking in real time and everything is recorded.

Or you can just record a message for students for them to answer at homework and they themselves can leave messages for anyone else, which means it's great for collaborative tasks as part of a wiki.

Plenty of scope some great activities, for example the classic jigsaw listening; each students has part of a story and questions which can only be answered by listening to everyone else.

Or just putting on a question which students discuss online, leaving their messages for other to pick up and follow up from. Perfect chance for students to practice those discussion skills and associated language.

Please do add other ideas...