1. Listen: Britney Spears, Nicki Minaj and Ke$ha's 'Till the World Ends' Remix

    April 23, 2011 12:19 AM EDT 0 0 0 B ritney Spears has called an impressive pop music summit by inviting Ke$ha and Nicki Minaj onto a remix of her latest "Femme Fatale" single, "Till the World Ends." The track leaked online late Friday (Apr. 22), before it was sch ...