The Collaborative International Dictionary of English v.0.48:

Canny \Can"ny\, Cannei \Can"nei\, a. [Cf. Icel. kenn skilled,
   learned, or E. canny. Cf. Kenn.] [North of Eng. & Scot.]
   1. Artful; cunning; shrewd; wary.
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   2. Skillful; knowing; capable. --Sir W. Scott.
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   3. Cautious; prudent; safe.. --Ramsay.
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   4. Having pleasing or useful qualities; gentle. --Burns.
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   5. Reputed to have magical powers. --Sir W. Scott.
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   No canny, not safe, not fortunate; unpropitious. [Scot.]
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WordNet (r) 3.0 (2006):

canny
    adj 1: showing self-interest and shrewdness in dealing with
           others; "a cagey lawyer"; "too clever to be sound" [syn:
           cagey, cagy, canny, clever]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "canny":
   Byzantine, Machiavellian, Machiavellic, Scotch, acute, adroit,
   arch, artful, astute, cagey, calculating, careful, cautious, chary,
   cheeseparing, circumspect, clever, conserving, crafty, cunning,
   cute, deceitful, deep, deep-laid, deliberate, designing, devious,
   dexterous, diplomatic, discreet, economic, economical, economizing,
   feline, forehanded, foxy, frugal, gingerly, guarded, guileful,
   heedful, hep, hesitant, ingenious, insidious, inventive, judicious,
   knowing, labor-saving, leaving out nothing, mindful, money-saving,
   nimble-witted, noncommittal, on guard, overlooking no possibility,
   parsimonious, pawky, penny-wise, politic, provident, prudent,
   prudential, quick, quick-witted, ready, regardful, resourceful,
   safe, saving, scheming, scrimping, serpentine, sharp, sharp-witted,
   shifty, shrewd, skimping, slick, slim, slippery, slow to act, sly,
   smart, smooth, snaky, sneaky, sophistical, spare, sparing,
   stealthy, strategic, subtile, subtle, supple, tactical, tentative,
   thorough, thrifty, time-saving, trickish, tricksy, tricky,
   unadventurous, uncommunicative, undaring, unenterprising,
   unprecipitate, unwasteful, vulpine, wary, wily