The Collaborative International Dictionary of English v.0.48:

Inventive \In*vent"ive\, a. [Cf. F. inventif.]
   Able and apt to invent; quick at contrivance; ready at
   expedients; as, an inventive head or genius. --Dryden. --
   In*vent"ive*ly, adv. -- In*vent"ive*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inventiveness
    n 1: the power of creative imagination [syn: inventiveness,
         ingeniousness, ingenuity, cleverness]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "inventiveness":
   Italian hand, acuteness, art, artfulness, artifice, astuteness,
   authenticity, cageyness, callidity, canniness, cleverness, craft,
   craftiness, creativeness, creativity, cunning, cunningness,
   fecundity, fertile mind, fertility, fine Italian hand, finesse,
   foxiness, freshness, gamesmanship, guile, ingeniousness, ingenuity,
   innovation, insidiousness, invention, newness, nonimitation,
   novelty, one-upmanship, originality, pregnant imagination,
   productivity, prolificacy, readiness, resourcefulness,
   satanic cunning, sharpness, shiftiness, shrewdness, slipperiness,
   slyness, sneakiness, sophistry, stealth, stealthiness, subtilty,
   subtleness, subtlety, suppleness, teeming imagination, trickiness,
   uniqueness, wariness, wiles, wiliness, wit