WordNet (r) 3.0 (2006):

fourth estate
    n 1: the press, including journalists, newspaper writers,
         photographers

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "fourth estate":
   AP, Associated Press, Fleet Street, Reuters, UPI,
   United Press International, advice, book publishing,
   broadcast journalism, communications, communications industry,
   information, intelligence, journalism, magazine publishing, news,
   news agency, news medium, news service, newsiness, newsletter,
   newsmagazine, newspaper, newsworthiness, press association,
   print medium, public press, public print, publishing,
   publishing industry, radio, reportage, telegraph agency,
   television, the fourth estate, the press, tidings, wire service,
   word