Hollywood Forever summer screening: http://www.cinespia.org/

Cinespia runs a summer film series hosted by the Hollywood Forever Cemetery that is incredible. Bring food and wine and sit amongst the graves to watch classics like North by Northwest, Purple Rain or Invasion of the Body Snatchers. 

Vineland drive in: http://www.vinelanddriveintheater.com/

Twenty minutes east of downtown LA is Vineland Drive-in, a fourplex outdoor theater showing all of the latest flicks as double bills.  The admission is cheap and the place is almost never packed.  Bring food, chairs and wine and really relax.

Hollywood Bowl: http://www.hollywoodbowl.com/

The Hollywood Bowl hosts sing-alongs that have become increasingly popular.  And of course people love to dress up when they attend The Sound of Music or Grease.  And nowhere is nicer to see anything outdoors, be it live music or movies, than the Hollywood Bowl. 

Los Angeles Film Festival/Ford Amphitheater: http://www.filmthreat.com/festivals/21925/

The Los Angeles Film Festival is one of the leading festivals in the world and to see movies before they are picked up by a distributor is always a great thing.  To be able to do it sitting comfortably outside at the Ford amphitheater just takes it over the top.