VoiceThread

Voicethread is a collaborative space of group conversations.
The example below is created by a student called Zoe in America, she designed it around her interest in Global Warming.

Zoe's Global Warming Voicethread

A VoiceThread can be created using documents, videos and photos. Comments can be added by registered users by text or voice.

They can be exported to your computer as a widescreen movie and to wikis, blogs and webpages. You can use a variety of images: JPG, GIF, BMP, PNG; docs: PPT, PPS, PDF, DOC, XLS; and videos. If you've got a Flickr account, you can import from those as well.
It has a 'doodle' feature which means you can draw over the images to make a point while you are recording your voice.
Classroom Application:
a way for children within the class to collaboratively present

• an investigation
• book report
• any writing genre (recounts, reports, explanations, descriptions, procedural etc)
  
• technology challenge

Or for children as in Zoe's example to invite experts outside of the classroom environment to comment or answer questions