*EDIT* Looks like JS beat me to it 
Right hand mouse click on the node, and press: Select objects with material assigned.
I don't have Maya open so I can't check for the exact wording, but you should be able to tell.
www.stevenegan-cgi.com
"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
"Yes."
[long pause] "Friend!!"