Major media conglomerates and a selection of holdings, plus their 2003 revenue.
(Excludes music and book publishing.)

TimeWarner - $39.6 billion
Holdings: Warner Bros, AOL, CNN, HBO, Time Warner Cable, Turner, Cartoon Network, The WB, New Line Cinema, Castle Rock Entertainment, DC Comics, People, Entertainment Weekly

The Walt Disney Company - $28.4 billion
Holdings: ABC, Disney Channel, ESPN, A&E, History Channel, E! Entertainment, Buena Vista, Touchstone Pictures, 10 TV stations, 60-plus radio stations, Miramax Films, and theme parks.

Viacom - $26.6 billion
Holdings: CBS and UPN networks, over 35 TV stations, MTV, Showtime, Nickelodeon, BET, Paramount Pictures, Blockbuster Video

News Corporation - $17.5 billion
Holdings: FOX Network, DirecTV, 34 TV stations, National Geographic Channel, FX, 20th Century Fox, the New York Post, The Times (of London)

NBC Universal (spinoff of GE) - $13 billion
Holdings: NBC, Telemundo, Universal Pictures, Universal Parks & Resorts, USA Network, CNBC, Bravo, MSNBC, PAX, 14 TV stations, Sci-Fi Channel

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Source: Columbia Journalism Review's Who Owns What?