There's been a lot of talk lately about the Big Three US automakers, and in my internet travels I've found a few more "Big" companies. 

Big Three automakers - Chrysler, Ford, GM
Big Four record labels - EMI, Sony BMG, Universal, Warner
Big Four TV networks - ABC, CBS, Fox, NBC
Big Four cell providers - AT&T, Sprint, T-Mobile, Verizon
Big Six movie studios - Disney, Fox, Paramount, Sony, Universal, Warner #business