Five-person a capella group Pentatonix, who won Season 3 of NBC's The Sing-Off, have just done this amazing medley of their favorite songs throughout history. They start with an 11th century madrigal, and granted they get to the 20th Century really fast, but wait til you hear their condensed version of the 2000s.
Also, they're on tour in the Pacific Northwest this spring, and maybe they'll be down here at some point.