The institution of graduate students' conferences seems to be rather wide spread (and I'm not sure whether there are really benefits of them that go beyond and/or add to to the benefits of having graduate students present papers at "normal" conference).
 
However: now there is an announcement/CfP for The Birkbeck Early Modern Society’s Third Student Conference: "Revolution and Evolution" (see http://www.emintelligencer.org.uk/2009/05/13/revolution-and-evolution-our-3rd-st udent-conference/ ), which apparently is not restricted to just graduate students. If this is so: this seems to be an interesting format/concept.  
Is such a thing done only at Birkbeck, or also in other places?
What are the experiences with it?
Should we try to start such a thing here. at our institute too?