The Collaborative International Dictionary of English v.0.48:

To-day \To-day"\, adv. [AS. t[=o] d[ae]g. See To, prep., and
   Day.]
   On this day; on the present day.
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         Worcester's horse came but to-day.       --Shak.
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The Collaborative International Dictionary of English v.0.48:

To-day \To-day"\, n.
   The present day.
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         On to-day
         Is worth for me a thousand yesterdays.   --Longfellow.
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WordNet (r) 3.0 (2006):

today
    adv 1: in these times; "it is solely by their language that the
           upper classes nowadays are distinguished"- Nancy Mitford;
           "we now rarely see horse-drawn vehicles on city streets";
           "today almost every home has television" [syn:
           nowadays, now, today]
    2: on this day as distinct from yesterday or tomorrow; "I can't
       meet with you today"
    n 1: the present time or age; "the world of today"; "today we
         have computers"
    2: the day that includes the present moment (as opposed to
       yesterday or tomorrow); "Today is beautiful"; "did you see
       today's newspaper?"

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "today":
   as of now, as things are, at present, at this juncture,
   at this moment, at this point, at this time, but now,
   contemporaneity, contemporaneousness, even now, for the nonce,
   for this occasion, here, here and now, hereat, hic et nunc,
   historical present, in our time, in these days, just now,
   modernity, newness, now, nowadays, nowness, on the spot, our times,
   present, present tense, presently, presentness, the Now Generation,
   the nonce, the now, the present, the present age, the present day,
   the present hour, the present juncture, the present time,
   the time being, the times, these days, this day, this hour,
   this instant, this moment, this night, this point, this stage,
   tonight