Sometimes when I am on the computer or just doing other things I put on a movie to kinda half watch. Obviously its not a movie thats really deep and just has a lot of action. My favorite backround movie is Die Another Day, its got great action and music.

Rounders, especially when I'm playing poker.

I never put on a movie just to have background noise--music sure, but not movies.

I check for delamination/rot on a regular basis. this is done by playing older dvds...though you dont have to sit there and watch every minute of it. you'll know when it screws up. right now...I'm at the computer and Natural Born Killers, one of my first dvds...is on in the background. I try to test older dvds at least once or twice a week.

Any kind of movie with audio commentary in it. I have a hard time to get asleep lately and I found them to be (uhh... yeah...) relaxing and it helps me to fall asleep.

City of Angels with the music-only track turned on. This is especially nice since there has yet to be a CD release of the score.

The Hunt for Red October and Contact. JFK is good to listen to as well

The Time Machine (both) & Crimson Tide

I do this a lot, since my entertainment center is right next to my computer desk... so it's easy to just turn my head slightly to the right and watch any scene that I partucularly like.

Let's see, my favourites to put in...

The Crow
Braveheart
Eddie Izzard: Dress To Kill
Caddyshack
Lethal Weapon 1-4
Meatloaf: VH1 Storytellers
Henry Rollins: Up For It
Henry Rollins: Talking From The Box / Henry Goes To London
South Park - Bigger, Longer & Uncut

Probably a few others, but those are the ones that come to mind right away.

Conan The Barbarian & Jaws - probably my most used backround, movies.

Music video DVDs, or better yet, isolated scores. Films are too involving for me to be really 'background'.

I usually have the habit of playing recently purchased DVDs as background. And something with audio commentary is another instance I do that as well.

Last of the Mohicans
Princess Bride

Big Lebowski

and

pr0n

empire records.

The Big Lebowski and Swingers. I could watch (or not) those movies a thousand times!

Orgazmo

Mel Gibson Payback or my LD of the Georgio Moroder Metropolis

Hackers I really like the soundtrack in that one plus its one of my favorite movies probably seen it 100+ times

Toy Story effects track.

South Park Bigger Longer & Uncut

Fight Club

Seven Samurai

It's a long movie and it's got tons of re-watch value to me.

I'll listen to a commentary track while making dinner, cleaning, etc - but never "watch" a movie while I'm doing other things.

Run these while I am at work:

South Park - BLU
Hackers
Lebowski
Half Baked
Dumb and Dumberer
Office Space
Happy Gilmore
Undercover Brother
Rounders
O Brother, Where Art Thou?

as well as others, but those are my primaries as they are ones that I have seen a bunch and dont need the picture to get the full enjoyment out of the movie since I can imagine it just by the dialog.