AddressReport: ranks landlords/neighborhood/local amenities.
Streeteasy.com -- advanced search tools including searching by commute time.
UrbanEdgeNY.com -- no fee apartment listings directly from landlords.
InsideDigs -- connects you to the current apartment occupants of units up for rent.
NYBits.com -- aggregates units for rent from other sites.
NakedApartments.com -- landlords/brokers pay monthly fee, but renters do not pay to search. Allows for reviews of brokers.
Craigslist.com -- elder of the bunch, narrow search by borough.
Trulia -- Trulia is an all-in-one real estate site that gives you the local scoop about homes for sale, apartments for rent, neighborhood insights, and real estate markets.
Padmapper -- plots listings, depends on current data; gives you a sense of cost variations
RentQuo.comRentQuo.com -- personal concierges find your perfect apartment based on your lifestyle, friends, and hobbies.
getoliver.comgetoliver.com -- app for apartment hunting
padspin.com -- I also found out about another one, but very few listings in PS :
Other resources:
Curbed.com -- good for real estate gossip
PSP member reviews of local real estate brokers and agents