The Collaborative International Dictionary of English v.0.48:

Ashamed \A*shamed"\, a. [Orig. a p. p. of ashame, v. t.]
   Affected by shame; abashed or confused by guilt, or a
   conviction or consciousness of some wrong action or
   impropriety. "I am ashamed to beg." --Wyclif.
   [1913 Webster]

         All that forsake thee shall be ashamed.  --Jer. xvii.
                                                  13.
   [1913 Webster]

         I began to be ashamed of sitting idle.   --Johnson.
   [1913 Webster]

         Enough to make us ashamed of our species. --Macaulay.
   [1913 Webster]

         An ashamed person can hardly endure to meet the gaze of
         those present.                           --Darwin.
   [1913 Webster]

   Note: Ashamed seldom precedes the noun or pronoun it
         qualifies. By a Hebraism, it is sometimes used in the
         Bible to mean disappointed, or defeated.
         [1913 Webster]

WordNet (r) 3.0 (2006):

ashamed
    adj 1: feeling shame or guilt or embarrassment or remorse; "are
           you ashamed for having lied?"; "felt ashamed of my torn
           coat" [ant: unashamed]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "ashamed":
   abashed, abject, blushing, chagrined, chapfallen,
   conscience-smitten, conscience-stricken, contrite, crestfallen,
   crushed, discomfited, embarrassed, full of remorse, hangdog,
   humbled, humiliated, mean, mortified, out of countenance, penitent,
   red-faced, regretful, remorseful, repentant, repining, rueful,
   self-accusing, self-condemning, self-convicting, self-debasing,
   self-flagellating, self-humiliating, self-punishing,
   self-reproaching, shamed, shamefaced, shamefast, shameful,
   sheepish, sorry, unhappy about, wistful