I'd go back and see Pink Floyd, Led Zeppelin, The Doors, The Rolling Stones and The Beatles LIVE when they were in their prime before Ticketmaster ruled the earth.
Then I'd love to see what kind of concerts they have on other planets.
Oh yeah, I'd also make sure to stop off in April 1938 and buy about 50 mint copies of Action Comics #1. (You know they're so rare because someone already went back in time and bought them all up)