WordNet (r) 3.0 (2006):

trailblazer
    n 1: someone who marks a trail by leaving blazes on trees
    2: someone who helps to open up a new line of research or
       technology or art [syn: pioneer, innovator,
       trailblazer, groundbreaker]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "trailblazer":
   adventurer, alpinist, ancestor, announcer, antecedent, astronaut,
   avant-garde, bellwether, buccinator, bushwhacker, camper, climber,
   coach, comers and goers, commuter, cosmopolite, cruiser,
   excursionist, explorer, fare, forebear, foregoer, forerunner,
   front runner, frontiersman, fugleman, globe-girdler, globe-trotter,
   goer, groundbreaker, guide, hajji, harbinger, herald, innovator,
   instructor, jet set, jet-setter, journeyer, lead runner, leader,
   mariner, mentor, messenger, mountaineer, palmer, passenger,
   passerby, pathfinder, pilgrim, pioneer, point, precedent,
   precursor, predecessor, preparationist, preparator, preparer,
   rubberneck, rubbernecker, sailor, scout, sightseer, stormy petrel,
   straphanger, teacher, tourer, tourist, trailbreaker, trainer,
   transient, traveler, trekker, tripper, vanguard, vaunt-courier,
   viator, visiting fireman, voortrekker, voyager, voyageur, wayfarer,
   world-traveler