The Collaborative International Dictionary of English v.0.48:

Complimentary \Com`pli*men"ta*ry\, a.
   Expressive of regard or praise; of the nature of, or
   containing, a compliment; as, a complimentary remark; a
   complimentary ticket. "Complimentary addresses." --Prescott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

complimentary
    adj 1: conveying or resembling a compliment; "a complimentary
           remark" [ant: uncomplimentary]
    2: costing nothing; "complimentary tickets"; "free admission"
       [syn: complimentary, costless, free, gratis(p),
       gratuitous]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "complimentary":
   acclamatory, admiring, adulatory, appreciative, approbatory, bland,
   blandishing, blarneying, buttery, cajoling, charitable,
   commendatory, congratulational, congratulatory, costless,
   courtierly, courtly, eleemosynary, encomiastic, eulogistic,
   expenseless, fair-spoken, fawning, fine-spoken, flattering,
   for free, for love, for nothing, free, free as air,
   free for nothing, free gratis, free of charge, free of cost,
   freebie, fulsome, giftlike, given, gratis, gratuitous, gratulant,
   gratulatory, gushing, honey-mouthed, honey-tongued, honeyed,
   insincere, insinuating, laudatory, mealymouthed, obsequious, oily,
   oily-tongued, on the house, panegyric, panegyrical, regardful,
   respectful, slimy, slobbery, smarmy, smooth, smooth-spoken,
   smooth-tongued, soapy, soft-soaping, sycophantic, unbought,
   unctuous, unpaid-for, untaxed, wheedling, without charge