My Neighbor Totoro purely for Paths of the Wind. There are so many variations of that song and I love them all. Also, this is kind of embarrassing, but I love Save the Last Dance's soundtrack. Other favs include Edward Scissorhands, Eternal Sunshine of the Spotless Mind, Amelie, The Music Lovers, Garden State (as much of a prick as Zack is I must admit he knows how to pick songs for movies -- pretty much the reason why Scrubs and that other movie he was in that I can't remember the name of had a great soundtrack), Pan's Labyrinth, The Lion King, Jurassic Park, Mulan, The Book of Eli purely for this, Dead Presidents, Shaft (original), Requiem for a Dream, and Black Swan.

I think the best film soundtracks though are the ones with purely original content, so that's why I respect films like say, Amelie more than a film like Dead Presidents or Black Swan since they use previously written things or renditions of things that have previously been recorded.