The Collaborative International Dictionary of English v.0.48:

So \So\, adv. [OE. so, sa, swa, AS. sw[=a]; akin to OFries,
   s[=a], s?, D. zoo, OS. & OHG. s?, G. so, Icel. sv[=a], sv?,
   svo, so, Sw. s?, Dan. saa, Goth. swa so, sw? as; cf. L. suus
   one's own, Skr. sva one's own, one's self. [root]192. Cf. As,
   Custom, Ethic, Idiom, Such.]
   1. In that manner or degree; as, indicated (in any way), or
      as implied, or as supposed to be known.
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            Why is his chariot so long in coming? --Judges v.
                                                  28.
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   2. In like manner or degree; in the same way; thus; for like
      reason; whith equal reason; -- used correlatively,
      following as, to denote comparison or resemblance;
      sometimes, also, following inasmuch as.
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            As a war should be undertaken upon a just motive, so
            a prince ought to consider the condition he is in.
                                                  --Swift.
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   3. In such manner; to such degree; -- used correlatively with
      as or that following; as, he was so fortunate as to
      escape.
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            I viewed in may mind, so far as I was able, the
            beginning and progress of a rising world. --T.
                                                  Burnet.
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            He is very much in Sir Roger's esteem, so that he
            lives in the family rather as a relation than
            dependent.                            --Addison.
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   4. Very; in a high degree; that is, in such a degree as can
      not well be expressed; as, he is so good; he planned so
      wisely.
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   5. In the same manner; as has been stated or suggested; in
      this or that condition or state; under these
      circumstances; in this way; -- with reflex reference to
      something just asserted or implied; used also with the
      verb to be, as a predicate.
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            Use him [your tutor] with great respect yourself,
            and cause all your family to do so too. --Locke.
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            It concerns every man, with the greatest
            seriousness, to inquire into those matters, whether
            they be so or not.                    --Tillotson.
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            He is Sir Robert's son, and so art thou. --Shak.
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   6. The case being such; therefore; on this account; for this
      reason; on these terms; -- used both as an adverb and a
      conjuction.
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            God makes him in his own image an intellectual
            creature, and so capable of dominion. --Locke.
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            Here, then, exchange we mutually forgiveness;
            So may the guilt of all my broken vows,
            My perjuries to thee, be all forgotten. --Rowe.
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   7. It is well; let it be as it is, or let it come to pass; --
      used to express assent.
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            And when 't is writ, for my sake read it over,
            And if it please you, so; if not, why, so. --Shak.
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            There is Percy; if your father will do me any honor,
            so; if not, let him kill the next Percy himself.
                                                  --Shak.
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   8. Well; the fact being as stated; -- used as an expletive;
      as, so the work is done, is it?
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   9. Is it thus? do you mean what you say? -- with an upward
      tone; as, do you say he refuses? So? [Colloq.]
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   10. About the number, time, or quantity specified;
       thereabouts; more or less; as, I will spend a week or so
       in the country; I have read only a page or so.
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             A week or so will probably reconcile us. --Gay.
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   Note: See the Note under Ill, adv.
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   So . . . as. So is now commonly used as a demonstrative
      correlative of as when it is the puprpose to emphasize the
      equality or comparison suggested, esp. in negative
      assertions, and questions implying a negative answer. By
      Shakespeare and others so . . . as was much used where as
      . . . as is now common. See the Note under As, 1.
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            So do, as thou hast said.             --Gen. xviii.
                                                  5.
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            As a flower of the field, so he flourisheth. --Ps.
                                                  ciii. 15.
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            Had woman been so strong as men.      --Shak.
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            No country suffered so much as England. --Macaulay.
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   So far, to that point or extent; in that particular. "The
      song was moral, and so far was right." --Cowper.

   So far forth, as far; to such a degree. --Shak. --Bacon.

   So forth, further in the same or similar manner; more of
      the same or a similar kind. See And so forth, under
      And.

   So, so, well, well. "So, so, it works; now, mistress, sit
      you fast." --Dryden. Also, moderately or tolerably well;
      passably; as, he succeeded but so so. "His leg is but so
      so." --Shak.

   So that, to the end that; in order that; with the effect or
      result that.

   So then, thus then it is; therefore; the consequence is.
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WordNet (r) 3.0 (2006):

so far
    adv 1: used in negative statement to describe a situation that
           has existed up to this point or up to the present time;
           "So far he hasn't called"; "the sun isn't up yet" [syn:
           so far, thus far, up to now, hitherto,
           heretofore, as yet, yet, til now, until now]
    2: to the degree or extent that; "insofar as it can be
       ascertained, the horse lung is comparable to that of man";
       "so far as it is reasonably practical he should practice
       restraint" [syn: insofar, in so far, so far, to that
       extent, to that degree]
    3: used after a superlative; "this is the best so far"; "the
       largest drug bust yet" [syn: so far, yet]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "so far":
   after a fashion, already, appreciably, as yet, at any rate,
   at best, at least, at most, at the least, at the most,
   at the outside, at worst, by this time, comparatively, detectably,
   earlier, fairly, heretofore, hereunto, hitherto, in a manner,
   in a way, in part, in some measure, incompletely, leastwise,
   merely, mildly, moderately, modestly, not comprehensively,
   not exhaustively, only, part, partially, partly, pro tanto, purely,
   relatively, simply, somewhat, still, then as previously, thus far,
   till now, to a degree, to date, to some degree, to this day,
   tolerably, until now, until this time, up to now, visibly, yet