Back in May Skype introduced five way calling as a beta product for Windows. Apparently the testing went well enough that today they introduced ten way video calling. Ten way calling is a Windows only beta product. You can read more about it here or download it here.

Applications for Education
Ten way calling could be used to connect classrooms for mini-global conferences. Ten way calling could also be used to host group study sessions online.

Here are some related resources that may be of interest to you:
Connecting Classrooms Through VoiceThread
A Simple Guide to Google Video Chat
3 Ways Other than Skype to Bring Experts Into Class