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.
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            And doth employ her economic art
            And busy care, her household to preserve. --Sir J.
                                                  Davies.
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   3. Managing with frugality; guarding against waste or
      unnecessary expense; careful and frugal in management and
      in expenditure; -- said of character or habits.
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            Just rich enough, with economic care,
            To save a pittance.                   --Harte.
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   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.
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            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.
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   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):

economic
    adj 1: 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]
    2: of or relating to the science of economics; "economic theory"
    3: 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]
    4: concerned with worldly necessities of life (especially
       money); "he wrote the book primarily for economic reasons";
       "gave up the large house for economic reasons"; "in economic
       terms they are very privileged"
    5: financially rewarding; "it was no longer economic to keep the
       factory open"; "have to keep prices high enough to make it
       economic to continue the service"

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "economic":
   Scotch, budget, budgetary, canny, careful, chary, cheap,
   cheeseparing, commercial, conserving, easy, economizing, economy,
   financial, fiscal, forehanded, frugal, inexpensive, labor-saving,
   low, low-priced, manageable, mercantile, moderate, modest,
   monetary, money-saving, nominal, parsimonious, pecuniary,
   penny-wise, politico-economic, productive, profitable, provident,
   prudent, prudential, reasonable, remunerative, saving, scrimping,
   sensible, shabby, shoddy, skimping, socio-economic, solvent, spare,
   sparing, thrifty, time-saving, token, trade, unexpensive,
   unwasteful, within means, worth the money