The Collaborative International Dictionary of English v.0.48:

Economic \E`co*nom"ic\ (?; 277), Economical \E`co*nom"ic*al\, a.
   [F. ['e]conomique, L. oeconomicus orderly, methodical, Gr. ?
   economical. See Economy.]
   1. Pertaining to the household; domestic. "In this economical
      misfortune [of ill-assorted matrimony.]" --Milton.
      [1913 Webster]

   2. Relating to domestic economy, or to the management of
      household affairs.
      [1913 Webster]

            And doth employ her economic art
            And busy care, her household to preserve. --Sir J.
                                                  Davies.
      [1913 Webster]

   3. Managing with frugality; guarding against waste or
      unnecessary expense; careful and frugal in management and
      in expenditure; -- said of character or habits.
      [1913 Webster]

            Just rich enough, with economic care,
            To save a pittance.                   --Harte.
      [1913 Webster]

   4. Managed with frugality; not marked with waste or
      extravagance; using the minimum of time or effort or
      resources required for effectiveness; frugal; -- said of
      acts; saving; as, an economical use of money or of time;
      an economic use of home heating oil. [WordNet sense 3]
      [1913 Webster + WordNet 1.5]

   5. of or pertaining to the national or regional economy;
      relating to political economy; relating to the means of
      living, or the resources and wealth of a country; relating
      to the production or consumption of goods and services of
      a nation or region; as, economic growth; economic
      purposes; economical truths; an economic downturn.
      [1913 Webster]

            These matters economical and political. --J. C.
                                                  Shairp.
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            There was no economical distress in England to
            prompt the enterprises of colonization. --Palfrey.
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            Economic questions, such as money, usury, taxes,
            lands, and the employment of the people. --H. C.
                                                  Baird.
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   6. Regulative; relating to the adaptation of means to an end.
      --Grew.
      [1913 Webster]

   7. of or pertaining to economics. economic theory
      [WordNet 1.5]

   8. profitable. Opposite of uneconomic. [WordNet sense 4]
      [WordNet 1.5 +PJC]

   9. avoiding waste; as, an economical meal. Opposite of
      wasteful.

   Syn: frugal, scotch, sparing, stinting, thrifty.
        [WordNet 1.5]

   Note: Economical is the usual form when meaning frugal,
         saving; economic is the form commonly used when meaning
         pertaining to the management of a household, or of
         public affairs.
         [1913 Webster]

WordNet (r) 3.0 (2006):

economical
    adj 1: using the minimum of time or resources necessary for
           effectiveness; "an economic use of home heating oil"; "a
           modern economical heating system"; "an economical use of
           her time" [syn: economic, economical]
    2: of or relating to an economy, the system of production and
       management of material wealth; "economic growth"; "aspects of
       social, political, and economical life" [syn: economic,
       economical]
    3: avoiding waste; "an economical meal"; "an economical
       shopper"; "a frugal farmer"; "a frugal lunch"; "a sparing
       father and a spending son"; "sparing in their use of heat and
       light"; "stinting in bestowing gifts"; "thrifty because they
       remember the great Depression"; "`scotch' is used only
       informally" [syn: economical, frugal, scotch,
       sparing, stinting]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "economical":
   Scotch, budget, canny, careful, chary, cheap, cheeseparing, close,
   conservative, conserving, easy, economic, economizing, economy,
   forehanded, frugal, inexpensive, labor-saving, low, low-priced,
   manageable, mean, miserly, moderate, modest, money-saving,
   niggardly, nominal, parsimonious, penny-pinching, penny-wise,
   penurious, politico-economic, provident, prudent, prudential,
   reasonable, saving, scrimping, sensible, shabby, shoddy, skimping,
   socio-economic, spare, sparing, stingy, thrifty, tight,
   tight-fisted, time-saving, token, unexpensive, unwasteful,
   within means, worth the money