ii'm a virgin to nyc.. but i'm going shopping next weekend !!!

where are some nice boutiques and stores to go? i already know of century 21.. but what else have some good deals and very nice clothing and accesories... besides the high ends stores (saks, neiman..etc) that i can find back here in boston.
is it true that if your lucky.. you can FIND real designer bags and whatever from ppl on the street?