WordNet (r) 3.0 (2006):

smidgen
    n 1: a tiny or scarcely detectable amount [syn: shred,
         scintilla, whit, iota, tittle, smidgen,
         smidgeon, smidgin, smidge]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "smidgen":
   ace, atom, bit, dab, dole, dot, dram, dribble, driblet, dwarf,
   farthing, fleck, flyspeck, fragment, gobbet, grain, granule, groat,
   hair, handful, iota, jot, little, little bit, lota, minim, minimum,
   minutiae, mite, modicum, molecule, mote, nutshell, ounce, particle,
   pebble, pinch, pittance, point, ray, scruple, smitch, speck,
   spoonful, spot, thimbleful, tiny bit, tittle, trifling amount,
   trivia, whit