The mixtape that Star-Lord carries around in Guardians of the Galaxy is of course available as an actual album (Amazon mp3, iTunes). The album isn't on Spotify, but there is a playlist of all the songs.
As Slate notes, the movie merch album isn't totally true to the movie as it includes two songs from Awesome Mix Vol. 2, but I will never complain of Marvin Gaye's or the Jackson 5's inclusion in anything.