The Collaborative International Dictionary of English v.0.48:

Naivet'e \Na`["i]ve`t['e]"\, n. [F. See Na["i]ve, and cf.
   Nativity.]
   1. The state or quality of being naive; lack of
      sophistication or worldliness.

   Syn: naivete, naiveness.
        [1913 Webster + WordNet 1.5 + PJC]

              A story which pleases me by its na["i]vet['e] --
              that is, by its unconscious ingenuousness. --De
                                                  Quincey.
        [1913 Webster]

   2. An act displaying naivete; a naive remark or action.
      [PJC] naivety

WordNet (r) 3.0 (2006):

naivete
    n 1: lack of sophistication or worldliness [syn: naivete,
         naivety, naiveness] [ant: mundaneness, mundanity,
         sophistication, worldliness]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "naivete":
   artlessness, bluffness, bluntness, candor, childlikeness,
   cullibility, deceivability, directness, dupability, easiness,
   greenness, guilelessness, gullibility, hoaxability, ingenuousness,
   innocence, naiveness, naivety, openheartedness, openness,
   outspokenness, persuadability, plainness, seduceability,
   simpleheartedness, simplemindedness, simpleness, simplicity,
   sincerity, single-heartedness, single-mindedness,
   singleness of heart, softness, trustfulness, unguardedness,
   unsophisticatedness, unsophistication, unsuspiciousness,
   unwariness, weakness