I like the obvious ones: Futurama, The Simpsons, Family Guy and South Park, but I can't belive nobody has mentioned my 2 of my all time favorites!
Space Ghost Coast 2 Coast - Its a tongue in cheek chat show presented by the star of 50's cartoon Space Ghost with real life guests that Space Ghost makes fun of. The real star of the show is Zorak (My Avatar!). He gets all the best lines until Space Ghost shoots him with his Lazer. This one is on Adult Swim (which is on Bravo in the UK).
The Mysterious Cities of Gold - My favorite from my childhood. Its based on 3 children searching for the cities of gold in South America at the time of the Spanish Conquistadors. Its better than i have made it sound... It as a Giant Golden Condor that they fly around in!