Today I tried out the Skype “group video” feature, and it works pretty well. It has, however, one serious drawback — in anything other than a 1:1 conversation, Skype’s screen sharing feature is disabled.
In casting about for a solution I found (or remembered a reference to) Join.me. Join.me allows screen sharing with upto 250 (!) other people, lets you grant control of your screen to them, and starts up a (toll call) teleconference bridge for everyone to use. All for free!