there's Dudes starring John Cryer, Flea and Lee Ving (of FEAR)
URGH! A Music War is the all encompassing punk-alt-wave movie of the early '80s spanning everyone from the Cramps to Pere Ubu to the Go Gos
Repo Man and Suburbia have been mentioned, but with Suburbia make sure to get the one from 1983 NOT 1996, two different films entirely
I'd say Rock & Roll High School as it's punk in attitude although Johnny Ramone himself questioned why everyone insisted that the Ramones were a "punk" band.
There is a newer movie called"This Is England" that focused on the trials and tribulations of a group of "Trad" ( non racist, ska loving) Skinheads and their separation as one of them became involved in the National Front , later a 4 part made for TV series called "This Is England '86 " picked back up on the characters 3 years down the road. both are wonderful.
"The Filth And The Fury" chronicles the rise and fall of the Sex Pistols and "Control" is a film about Ian Curtis and Joy Division. 24 Hour Party People tells the story of the Manchester scene and Factory records from the disenchanted 1978 sounds of Cabaret Voltaire to the ecstasy fueled rave notions of the Happy Mondays.