The Collaborative International Dictionary of English v.0.48:

Mindful \Mind"ful\, a.
   Bearing in mind; regardful; attentive; heedful; observant.
   [1913 Webster]

         What is man, that thou art mindful of him? --Ps. viii.
                                                  4.
   [1913 Webster]

         I promise you to be mindful of your admonitions.
                                                  --Hammond.
   [1913 Webster] -- Mind"ful*ly, adv. -- Mind"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mindful
    adj 1: bearing in mind; attentive to; "ever mindful of her
           health"; "mindful of his responsibilities"; "mindful of
           these criticisms, I shall attempt to justify my action"
           [syn: mindful, aware] [ant: forgetful, mindless,
           unmindful]

Moby Thesaurus II by Grady Ward, 1.0:

160 Moby Thesaurus words for "mindful":
   accommodating, accommodative, active, advertent, agog, agreeable,
   alert, alive, alive to, all ears, all eyes, all-knowing,
   apperceptive, appercipient, appreciative of, apprehending,
   apprehensive, apprised of, assiduous, attentive, au courant, awake,
   awake to, aware, aware of, behind the curtain, behind the scenes,
   canny, careful, cautious, circumspect, cognizant, cognizant of,
   complaisant, compliant, comprehending, concentrated, conforming,
   conscientious, conscious, conscious of, considerate, constant,
   conversant, curious, deliberate, delicate, devoted, devout,
   diligent, discreet, duteous, dutiful, earnest, evocative, faithful,
   finical, finicking, finicky, gingerly, guarded, haunted, heedful,
   helpful, hep to, hesitant, in retrospect, in the know,
   in the secret, indulgent, informed of, insightful, intelligent,
   intense, intent, intentive, judicious, knowing, knowledgeable,
   leaving out nothing, lenient, let into, loving, loyal, memoried,
   meticulous, mindful of, mindful of others, mnemonic, nagged, nice,
   niggling, no stranger to, noncommittal, obliging, observant,
   observing, obsessed, omniscient, on guard, on the ball, on the job,
   on the lookout, on to, open-eared, open-eyed, openmouthed,
   overlooking no possibility, pawky, perceptive, percipient,
   perspicacious, plagued, politic, practicing, prehensile, privy to,
   prudent, punctilious, punctual, rankled, redolent, regardful,
   remembering, remindful, reminiscent, retentive, retrospective,
   safe, sagacious, scrupulous, seized of, sensible, sensible of,
   sensible to, shrewd, slow to act, solicitous, streetwise,
   suggestive, tactful, tender, tentative, thorough, thoughtful,
   tolerant, true, unable to forget, unadventurous, uncommunicative,
   undaring, undeceived, understanding, unenterprising, unmindful,
   unprecipitate, vigilant, watchful, wise, wise to