The Castle Of Cagliostro is a fantastic movie. Inspired by a recent Miyazaki thread, I recently watched two TV series directed by him:

- Future Boy Conan

- Lupin III (partly Miyizaki, partly Takahata, partly other directors)

Lupin III was ok, but I wouldn't particularly recommend it (the TV series, as mentioned the film is excellent). But I would wholeheartedly recommend Future Boy Conan (also known as "Conan, The Boy in Future"). I thought this was every bit as good as his movies, with the bonus that it's almost 13 hours long in total.