I use more mp3's than anything else, so some of this may not be valid for albums. I use movies, video games (both console & computer), classical music, anime, and various albums as sources:
13th Warrior
The Abyss
Akira
Alice (McGee's version)
Alien
Alien vs. Predator
Babylon 5
Baldur's Gate (& 2)
Battlestar Galatica
Belioz's Symphonie Fantastique
Black & White
Bram Stoker's Dracula
Brian Eno
The Brotherhood of the Wolf
Conan the Barbarian
Diablo (& 2)
Dragon Quest
Dragon Warrior (reorchestrated)
Dungeon Keeper
Echos of Nature (nature soundtracks)
Escaflowne (this has some GREAT tracks)
Excalibur
Final Fantasy (most of the games have orchestrated tracks available for purchase that are quite good and nostalgic)
Ghost in the Shell
Gladiator
Grieg's Peer Gynt Suite
Icewind Dale
Mediaeval Baebes
Merlin's Magic
Midnight Syndicate (these guys are awesome)
The Mummy
Mussorgsky's Night on Bald Mountain
Mussorgsky's Pictures at an Exhibition
Myst III
Neverwinter Nights
The Ninth Gate
Orff's Carmina Burana
Paul O'Dette
Planescape Torment
Pool of Radiance
Princess Mononoke (again, GREAT tracks)
Sacrifice
Signs
Skies of Arcadia
Star Trek TNG: all four movie soundtracks
Stravinsky's Rite of Spring
Suikoden
Vangelis
Valkyrie Profile
Vivaldi's The Four Seasons
Wagner's Twilight of the Gods
Wagner's Valkyrie
Xena (they just released a six-cd set)
Xenogears