I like the ending music on Spaceship Earth, when you go by the city display as you go down the decent tunnel. It was a fantastic end to a fantastic and powerful ride. However, I've heard nothing but bad things about the end of the new ride, and I haven't been on it, so I can't tell if the music changed, but I remember it being very good as far as the last time I was on it.
Space Mountain has really cool music. I like going in the Fastpass line for this ride, because there is usually no one in it, so I can just stop or walk slowly in the tunnel and take all the cheesy 70's theming in and listen to the music. It's really sedated, and it's fun to listen to, especially riding the TTA.
And then there's the music in the SFNE Superman station, if you can actually hear it over the people waiting to ride.