The Hour Variety Show Channel: Laugh-In, Carol Burnette, Sonny & Cher, Sid Caesar, etc. There’s thousands of hours of this stuff that you virtually never see unless you buy it as home video sets.
The Lego Film Channel:
All the classics, interpreted as you’ve never seen them before (plastic with bumps on top). 
We could gather the Log Channel and the Fishtank Channel and other ‘visual background’ channels up into a family, which would include:
The Antfarm Channel
The Sheepfold Channel
The Forest Canopy Channel
and, last but definitely not least:
The Scenery Channel.
This last one will apparently be broadcasting in Hill Valley, California, by 2015. 
Other channels:
The Math Channel:
Animated math lessons and explanations, everything from 1+1=2 to differential calculus to all those things that Mathochist and the others discuss here on the boards. Includes lots of pretty pictures and sounds to show how deeply math and art are connected.
The Student Film Channel:
This would show the experimental videos and films that the students make at schools like Sheridan College, the sort of thing that gets shown once at the school assemby and then archived forever more. We will add student films made at places outside the film-school system as well.
Brother to this channel will be The Short Animation Channel, which will show experimental and international films such as the National Film Board shorts that win Oscars but never show up on TV or in theatres because they don’t ‘fit the format’.
The Internet Animation Channel:
All those five-minute flash animations that surge across the net one week and then are gone the next? See them here. Includes Weebl and Bob, the Numa Numa song, Salad Fingers, Smoking Kills, Red versus Blue, and countless others.
BTW, this kind of thing is already happening on internet radio… I’ve spent this evening dividing my listening among Radio Esperanto (music and commentary in Esperanto), Pagan Sounds (Pagan music, mostly celtic in flavour), and The ZZZone (anbient electronica). Video is only a matter of time…
Want to experience what schizophrenia’s like? Watch and listen to both at the same time!
Zyada suggested a belly-dance channel, which I thought was a little restrictive, so we decided on DIN - The Dance International Network, featuring performance and recreational dancing from around the world: belly dancing of course, flamenco, jigs and reels from all sorts of places, square dancing, Fred Astaire and all those other dance movies, …
I’ll also second the real-science network suggested above, and a real-history-not-just-WWII channel as well.
A show that had pro wrestling classics all day long.