The Collaborative International Dictionary of English v.0.48:

Announcer \An*noun"cer\, n.
   One who announces.
   [1913 Webster]

WordNet (r) 3.0 (2006):

announcer
    n 1: someone who proclaims a message publicly
    2: reads news, commercials on radio or television

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "announcer":
   AFTRA, DJ, MC, adviser, ancestor, anchor, anchor man, anchorman,
   annunciator, antecedent, authority, avant-garde, bellman,
   bellwether, broadcaster, buccinator, buccinator novi temporis,
   bushwhacker, channel, commentator, communicant, communicator,
   crier, disk jockey, emcee, enlightener, enunciator, expert witness,
   explorer, forebear, foregoer, forerunner, foreshadower,
   front runner, frontiersman, fugleman, gossipmonger, grapevine,
   groundbreaker, guide, harbinger, herald, informant,
   information center, information medium, informer, innovator,
   interviewee, lead runner, leader, master of ceremonies, messenger,
   monitor, mouthpiece, news commentator, newscaster, newsmonger,
   notifier, nunciate, pathfinder, pioneer, point, precedent,
   precursor, predecessor, premonitor, presager, presenter, press,
   proclaimer, program director, programmer, public relations officer,
   publisher, radio, radiobroadcaster, reporter, scout,
   sound-effects man, source, spokesman, sportscaster, stormy petrel,
   television, teller, tipster, tout, town crier, trailblazer,
   trailbreaker, vanguard, vaunt-courier, voortrekker, weatherman,
   witness