The Collaborative International Dictionary of English v.0.48:

Readily \Read"i*ly\ (r[e^]d"[i^]*l[y^]), adv.
   1. In a ready manner; quickly; promptly. --Chaucer.
      [1913 Webster]

   2. Without delay or objection; without reluctance; willingly;
      cheerfully.
      [1913 Webster]

            How readily we wish time spent revoked! --Cowper.
      [1913 Webster]

WordNet (r) 3.0 (2006):

readily
    adv 1: without much difficulty; "these snakes can be identified
           readily"
    2: in a punctual manner; "he did his homework promptly" [syn:
       promptly, readily, pronto]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "readily":
   agilely, agreeably, animatedly, anxiously, apace, ardently,
   at once, at short notice, avidly, breathlessly, charitably,
   cheerfully, de bonne volonte, eagerly, easily, effortlessly,
   enthusiastically, expeditiously, facilely, freely, gladly,
   graciously, hands down, happily, immediately, impatiently,
   in no time, instantaneously, instanter, instantly, keenly, lightly,
   like clockwork, like nothing, nimbly, no sweat, on easy terms,
   on short notice, promptly, pronto, quickly, right away, simply,
   smoothly, speedily, spryly, swiftly, swimmingly, ungrudgingly,
   vivaciously, well, willingly, with a will, with alacrity,
   with dispatch, with good will, with gusto, with open arms,
   with relish, with zest, without delay, without difficulty,
   zealously, zestfully