Hello! I am a tech coordinator for a Minnesota public school. I've recently helped a couple of our 3rd grade math teachers begin a weekly "MathCast" episode, using voicethread.com.
It's completely student-created (except the teacher takes the photos). We've had great fun producing these!
You can check them out here
to get a feel for what we're doing...
I'd love to see us begin a collaborative project with students from, well, anywhere! It would be fun for our students to end their MathCast with a problem for YOUR students to solve. Your students could then log in and record their narration, giving the answer and an explanation of how they solved it.
Voicethread.com allows teachers to get the "pro" account for free! This account allows you to create up to 30 profiles with the same login. So, you could have a class login, and each student uses the same username/PW combo, but they can have their own profile for recording.
We don't go that far; I just have the students record in a single profile under my account, at least for now.
So, if you have any interest in this, please get in touch with me. It might be great fun!