Good site for downloading kids' movies?

I want to download (legally!!) some kids movies for my son - things like Mickey Mouse cartoons and I'm also looking for a flim called The Polar Express.  Can anyone recommend a good site for downloading kids movies that isn't too expensive? I'm not a big downloader so I haven't a clue really.

Thanks.

iTunes   They have Polar Express for sure!

See this is how clueless I am, I thought iTunes only did music.

They did up until last year or so (In the UK) I believe.  They have Mickey Mouse Club House for sure as well.