WordNet (r) 3.0 (2006):

freeloader
    n 1: someone who takes advantage of the generosity of others

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "freeloader":
   barnacle, beat, beggar, bloodsucker, bummer, cadger, caller,
   company, coupon clippers, deadbeat, deadhead, drone, free rider,
   frequenter, gate-crasher, guest, habitue, hanger-on, idle rich,
   leech, leisure class, lounge lizard, lumpen proletariat, mendicant,
   moocher, nonworker, panhandler, paper, paper house, parasite,
   pass holder, rentiers, smell-feast, spiv, sponge, sponger, sucker,
   the unemployable, the unemployed, uninvited guest, visitant,
   visitor, well