What about "Pictures at an Exhibition" by Modest Mussorgski? The original is written for piano. I love the Ravel version for Orchestra, the Emerson, Lake & Palmer version and the synthesizer version by Tomita. And there are a lot of other versions!
Big fan of Aaron Copland as well. If you can find "Quiet City," to me that's his best work. My high school's orchestra played it my senior year (I was in the orchestra but didn't play it, as I was percussion and the song has none).
A few others we played that I really like:
Copland's "Rodeo Suite" (We played Hoedown... more commonly known as the beef commercial song)
Holst's "The Planets" (Played Jupiter)
Vivaldi's "Four Seasons" (Played Summer)
Bach's "Brandenburg Concertos" (Played #2, I believe)
Also a big fan of Clint Mansell's "Lux Aeterna" AKA "Summer Overture" or the theme from Requiem for a Dream. It was remixed and put in stuff for Lord of the Rings, and used by Fox for the 2004 ALCS. I also used it for the background music of a news package in college on fire departments. The teacher said it was WAY too over the top, so I only got a B.