The Collaborative International Dictionary of English v.0.48:

Informative \In*form"a*tive\, a.
   Having power to inform, animate, or vivify. --Dr. H. More.
   [1913 Webster]

WordNet (r) 3.0 (2006):

informative
    adj 1: tending to increase knowledge or dissipate ignorance; "an
           enlightening glimpse of government in action"; "an
           illuminating lecture" [syn: enlightening,
           informative, illuminating] [ant: unenlightening,
           unilluminating]
    2: serving to instruct or enlighten or inform [syn:
       instructive, informative] [ant: uninstructive]
    3: providing or conveying information [syn: informative,
       informatory] [ant: uninformative]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "informative":
   advisory, autodidactic, coeducational, communicative, cultural,
   didactic, disciplinary, edifying, educating, educational,
   educative, elucidative, enlightening, exhortatory, explanatory,
   homiletic, hortatory, illuminating, informational, informing,
   initiatory, instructive, introductory, lecturing, monitory,
   preaching, preceptive, propaedeutic, revealing, self-teaching,
   teaching, tuitionary