I know for me, I enjoy to watch movies about mental illness as it is a learning tool for me. Please see below a list of movies and the particular mental illness they are related to. You may want to rent a few if your anything like me.

AIDS-related Psychosis
Angels in America (2003)
The Hours (2002)

Anterograde amnesia
Memento (2001)

Autism
Rain Man (1988) (

What's Eating Gilbert Grape? (1993)

Dissociative disorders
Fight Club (1999)
Me, Myself, and Irene (2000)
Nurse Betty (2000)
Passion of Mind (2000)
Secret Window (2004)
Sybil (1976)

Mental retardation
Bennie and Joon (1993)
Charly (1968)
I am Sam (2001)
Forest Gump (1994)
The Other Sister (1999)
Riding the Bus with my Sister (2005 - TV)

Mood disorders
The Hours (2003)
Mr. Jones (1993)
Pollock (2001)
Sylvia (2003) )

Obsessive compulsive disorder
As good as it Gets (1997)
The Aviator (2005)
Monk TV Series (2002- )

Personality disorders
Girl Interrupted (1999)

Schizophrenia
A Beautiful Mind (2002)
Clean Shaven (1995)
Donnie Darko (2001)
K-Pax (2001)
Joan of Arc (1999)
Julien Donkey-Boy (1999)
Madness of King George (1994)
The Shining (1980)
Spider (2002) Sexual taboos
Blue Sky (1994) )
Breaking the Waves (1996)
Quills (2001)

Stress disorders
Mrs. Dalloway (1997)

Miscellaneous & unspecified
The Butcher Boy (1998)
Conspiracy Theory (1997)
She's so Lovely (1997)
Shine (1996)
Patch Adams (1998)