As a classroom teacher you have inevitably heard this statement from your student..."Everytime I open this file it looks like it was written in Japanese". The issue is always that the file was created with a program at the student's house that we don't have at school or it was a Mac program and we have Windows machines, etc. In the past I have used Zamzar to convert these files but it has been blocked in our district for teachers so it is not a viable solution anymore. Online-ConVert seems to do it all and the fact that it is free and web-based make it a one stop solution. Recently on Tekzilla's Daily Tip (great website with daily video tech tips) they reviewed Online-ConVert which is where I learned about if for the first time.
This will prove to be a very valuable tool for you and your students. Add it to your webpage so that students can use it at home and maybe even save you the step of having to convert it at school. This can also be used to convert YouTube videos to .flv (flash video file) and then embedded into Smart Notebook.