When we built our house eight years ago I converted an upstairs bonus room into a home theater. At the time I installed a Panasonic PT-L300U but when I later upgraded to a 1080p projector I kept the 300u as a backup. It wasn't long before I discovered an alternative use for it...outdoor movies!
I first experimented with tacking up a king-sized bed sheet to the garage door frame and invited a few of my neighbors over to watch Monday Night Football. It worked so well that I decided the bed sheet wasn't big enough so I bought a roll of plain white, cotton fabric for about $40 from the fabric center at Wal-Mart that covers almost the entire frame of the garage door opening. I tack the fabric to the top of the garage door trim using push pins and then wrap the bottom of the fabric with a heavy, outdoor treated 2x4 to keep tension on the screen. The fabric is thin and works perfectly as reverse image projection screen. I am actually projecting the image on the inside of the screen but the fabric is so thin that the image shows up just as brightly on the opposite side. Basically what I am doing is turning our garage into a giant, rear-projection TV.
All that is needed for sound is an old Aiwa boombox. The empty garage amplifies the sound a lot so high amplification is not needed. It sounds great!
Here is a picture from inside the garage. The image appears backwards because I reversed the image in the projector settings so the picture appears correct from outside.
We watch sports on it from time to time but what has become a real tradition in our neighborhood is our annual Halloween Film Festival. We usually do it a week or two before Halloween and we show classic Halloween shorts like Donald Duck's "Trick or Treat", "It's the Great Pumpkin, Charlie Brown", Disney's "The Legend of Sleepy Hollow" cartoon, etc., and then show a Halloween or spooky-themed movie like "Scooby-Doo 2: Monsters Unleashed" or "Wallace & Gromit: Curse Of The Were-Rabbit". Nothing too scary for the kids but spooky just the same. Here are pictures from our Halloween setup. I set up a couple of rows of hay bales for the kids to sit on.
Here are the neighborhood kiddos watching a Halloween movie.