Big Blue Button is an open source web conferencing system for on-line learning. The Big Blue Button plugin activity enables you to:
Create video-conference activities within your course
Restrict Students from joining a session until a Teacher joins the session
Create a custom welcome message
Specify open/close dates - that appear in the Moodle calendar
Record a session
Access and mange recordings (requires recordingsbn plugin)
We're preparing a fully working demo of this activity plugin here, but for now you try the official Big Blue Button demo site http://demo.bigbluebutton.org to see how BBB itself works.