What about Jugglers?
Terry Teachout continues his "middlebrow" musings in response to the Blowhards posting on types of performers you don't see much anymore on TV. The list includes ventriloquists (Edgar Bergen, Senor Wences), Impersonators (Rich Little, Vaughn Meader, David Frye) and Comedy Teams (Martin & Lewis).
I would add Jugglers, Clowns (remember when Emmett Kelly was a celebrity), Popular Classical Singers (think Marnie Nixon), and Flamenco Dancers. All staples of Ed Sullivans past, but you would be hard pressed to find any of these on a mainstream TV show (with the exception of PBS).