Infinitely Polar Bear. Watched it for the second time yesterday. (I've actually been putting together a post about it today, but computer froze. Hopefully I can finish it tonight.)
I also liked
The Soloist with Jamie Fox playing a man with schizophrenia.
Another vote for
Benny and Joon. Sweet movie.
(Ye gawds, I hated SLP. But I shall refrain...

)