I don't know most of them personally. But I loooove the music of On A Sensual Note, American University's male a cappella group. So because they are so awesome, here are a few of my favorite videos of OASN, courtesy of the great YouTube.
Here they are singing "In the Jungle [The Lion Sleeps Tonight]" at Mr. Yogato, one of DC's greatest frozen yogurt shops:
And here is the classic song "Good Ol' A Cappella in AU's Katzen Arts Center:
And my favorite, from last year's Parents' Weekend concert, here is Michael Jackson's classic song "Thriller," complete with dance moves: