I've seen a little discussion on this topic inside of other threads intended for other topics, but I figured I'd start a dedicated thread.
Please post your favorite songs to demo new equipment, and possibly a few words on why or what you listen for (keep it short). I'll start.
Eva Cassidy, "What a wonderful world", Live at Blues Alley (for sub tonality and low end EQ)
Dr. John, "Janko Partner", Definitive Pop Collection (for detail)
James Taylor, "Steamroller Blues", The Best of James Taylor (for detail and sound stage)
Dave Brubeck, "This Masquerade is Over", Back Home (for overall integration and bass tonality)
Nate Dogg, "Lay Low" (for bass tightness/control)
Outkast, "The way you move", Speakerboxx (for bass extension)