Katy Perry, Usher and fun. have all been added to the growing list of performers who will participate in President Obama's inaugural events. Following yesterday's announcement that Beyoncé, James Taylor and Kelly Clarkson will perform at the ceremony itself, Perry, Usher, fun. and others have now been confirmed to play at various inaugural celebrations taking place on Jan. 21, as well as a children's concert on Jan. 19. Other acts who will lend their talents to the festivities include Smokey Robinson, John Legend, Alicia Keys, Stevie Wonder, Marc Anthony, and the cast of Glee.