The Collaborative International Dictionary of English v.0.48:

Unshackle \Un*shac"kle\, v. t. [1st pref. un- + shackle.]
   To loose from shackles or bonds; to set free from restraint;
   to unfetter. --Addison.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "unshackle":
   discharge, emancipate, liberate, loose, loosen, manumit, release,
   unbar, unbind, unbolt, unbridle, unbuckle, uncage, unchain,
   unfetter, ungag, unhandcuff, unhobble, unlash, unlatch, unleash,
   unlock, unloose, unloosen, unmanacle, unmuzzle, unpen, unpinion,
   unstrap, untether, untie, untruss, unyoke