WordNet (r) 3.0 (2006):

trendy
    adj 1: in accord with the latest fad; "trendy ideas"; "trendy
           clothes"; "voguish terminology" [syn: trendy,
           voguish]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "trendy":
   a la mode, all the rage, all the thing, coxcomb, current,
   exhibitionist, fashionable, flash, grandstander, groovy, hip, hot,
   in, in fashion, in style, in vogue, mod, modern, modish, new,
   newfashioned, now, popular, prevalent, show-off, smart, stylish,
   swank, swish, tony, ultramodern, up-to-date, up-to-datish,
   up-to-the-minute, voguish, with it, with-it