I know this isn't NYC related, but I just stumbled upon hotelcashback.com - a new blog that will try to alert you to any hotel deals that they have found. Currently, their selection isn't impressive, but it's a start.
They have listed:
$24.11 / night @ Stratosphere tower in Las Vegas, USA
$50.68 / night @ Sheraton Buganvilias Resort in Puerto Vallarta, Mexico
$93.54 / night @ Hawaii Prince Hotel Waikiki in Honolulu, USA