Among the nicest things about Youtube is certainly the splendid choice of animated short films. Here are some of my current favourites:
Of course there's Oktapodi, a hilarious film about the power of love. I can watch this one over and over!
Then also nice but a bit calmer is Going Green, a film about a traffic light fed up with it's daily work.
And finally something to think about: The Lost Thing. With nearly 16 minutes not really short, but definitely worth watching. Reminds me a bit of the art of Tinguely.