Circle of Life always brings back great memories for me. Also Part of Your World and Under the Sea. As of now, I really love the Tarzan soundtrack. Phil Collins is incredible. Also some of the newer stuff like from Tangled and Princess and the Frog, although not quite as good, still has that great Disney flavor to it. I also agree that if you want a darker flavor to it, Hunchback (ESPECIALLY Hellfire) is super intense and very good. Also don't forget Mary Poppins (yes, that's Disney): Step in Time, Supercalifragilisticexpialidocious, Chim-Chimney.
Everything from Mulan. Everything from Pocahontas (SAVAGES! SAVAGES!)
I could make a list out the door of all the great Disney songs. Basically, it's hard to find a bad Disney song if you're looking through the classic movies.