Star Wars: TPM - The pod race is orgasmically good and has some really low shit in it. Hell, all of Eps I & II are excellent on the ears, especially the fight/battle scenes.
Ice Age - there's this <20Hz "WHUUUMP!" I nearly took my house down with yesterday. Generally very good audio throughout, although that's the same with alot of CGI stuff - FF, Toy Story 2, Monsters Inc, Antz etc.
Minority Report - The pulse/sonic gun. Fuck me that's some tight shit!
U-571 - got some unbelievably low stuff in it. You might actually lose sphincter control during the depth charge scenes.
TitanAE - pretty phat bass all the way through.
Cast Away - the plane crash.
Saving Private Ryan - the beach landing and the bit at the end with the tanks... both have shitloads of LFE and make stuff fall off shelves. Also very good surround content throughout.
Fifth Element - the Diva sequence is pant-wettingly delicious.
Fast & The Furious - decent all-round workout.
The Matrix - the green WB splash at the beginning and the "WUUUUMP!" after he lays the smack down on Agent Smith are both good on a decent sub. The lobby scene and the bullet-time bits are amazing surround demos.
Apollo 13 - the launch. If you have decent kit your house will actually fall apart at this point.
Black Hawk Down - generally excellent audio throughout.
Those are the ones that spring immediately to mind. Have a look
here. Some good and bad suggestions there. Plus, download and run some of these if you have a PC hooked up:
http://www.cinenow.com/us/vobtrailer.php3