NUNS
Nuns are women who dedicate themselves to a lifetime of service, piety and obedience, and they have been the basis of many fine movies. 
A good place to begin is Doubt (2008). Meryl Streep is the Mother Superior at a parochial school, Amy Adams is a young and naive teacher and Phillip Seymour Hoffman is the good-natured parish priest suspected of unnatural behavior. This is heady company indeed, but virtual unknown Viola Davis almost steals the movie as the mother of the possible victim. The tension builds almost to the breaking point and to a frankly surprising ending. All four of the principals were nominated for Oscars, along with writer-director John Patrick Shanley. None of them won.
Perhaps no Hollywood film has captured what it must be like to become a nun as well as The Nun’s Story (1959). This fine movie captured eight Oscars, including Best Picture and Best Director (Fred Zinnemann). Audrey Hepburn also won for her portrayal of Sister Luke. Her training, discipline and service make a very good story. She becomes a medical nun in Africa under the tutelage of agnostic Dr. Fortunati (Peter Finch). 
From the sublime to the ridiculous, Whoopi Goldberg is on the run from her murderous mobster boyfriend and hiding out in a convent in Sister Act (1992). She shakes things up quite a bit as the hip new choir director and the laughs are plentiful. Not exactly a slice of life, but lots of fun. Beware the weak sequel.
A young nun may have become pregnant and may have murdered the baby in the enigmatic Agnes of God (1985). Jane Fonda, Meg Tilly and Anne Bancroft are all very good in a film with no easy answers. The opaque nature of the story line may turn some off, but the performances make it worth a look. 
A nun is the central figure in perhaps the best movie about capital punishment ever made, Dead Man Walking (1995). Susan Sarandon is Sister Helen Prejean, a devoted opponent of the death penalty. Sean Penn is the unlikeable object of her efforts. Actually quite fair and balanced on a sensitive subject about which everyone has an opinion. Ms. Sarandon won the Oscar as Best Actress. 
And finally I have to mention the wonderful off-Broadway play, Nunsense (1992), a howlingly funny send up of a very off-beat convent. None of the sequels are very good.
Oh, and we must remember that the accomplished Sally Field (Oscar winner for Norma Rae) got her start as The Flying Nun!
All of the films in this article are for grownups, and all are available on DVD.