The Collaborative International Dictionary of English v.0.48:

Enlightener \En*light"en*er\, n.
   One who enlightens or illuminates; one who, or that which,
   communicates light to the eye, or clear views to the mind.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "enlightener":
   adviser, announcer, annunciator, authority, channel, communicant,
   communicator, expert witness, gossipmonger, grapevine, informant,
   information center, information medium, informer, interviewee,
   monitor, mouthpiece, newsmonger, notifier, press,
   public relations officer, publisher, radio, reporter, source,
   spokesman, television, teller, tipster, tout, witness