891 Amsterdam Avenue, at 103rd Street
(212) 932 - 2300
This hostel is very popular amongst friends and guests of students at Columbia University.  Conference attendees have stayed here in the past, noting its comfortable accomodations and exceptionally reasonable prices.
Visit their website:   http://hinyc.citysearch.com/?cslink=  

Ellington Hotel

610 West 111th Street, between Broadway & Riverside Drive
(212) 864 - 7500
For reservations, call (888) 66 - HOTEL or (212) 644 - 6000  

Empire Hotel

4 West 63rd Street at Broadway
(212) 265 - 7400
For reservations call (800) 333 - 3333
http://www.empirehotel.com/  

Excelsior Hotel
 
45 W. 81st Street, between Columbus Avenue and Central Park West
(212) 362 - 9200
For Reservations call (800) 368 - 4575
http://www.excelsiorhotelny.com/  

Milburn Hotel

242 W. 76th St between Broadway & Riverside Drive
(212) 361 - 1010
For reservations call (800) 833 - 9622
http://www.milburnhotel.com/