NYC Open Data : Clearinghouse for data from all New York City agencies. Much of this data in this collection is already in GIS friendly formats.
BYTES of the Big Apple : Portal for the geographic datasets provided by the NYC Planning Department. Includes tax lots (Mappluto), various boundaries and facilities, and official street centerline (LION) files.
CoreData.nyc : Map based data hub for housing and neighborhood resources from NYU Furman Center for Real Estate and Urban Policy.
GeoData@Columbia : A wide variety of NYC specific datasets and maps can be found in our own collections.
GIS.NY.GOV - Spatial data clearinghouse for all state and county agencies. NOTE: much of this disparate collection is password protected and may require an appointment with DSSC staff for access. Contact us at email@example.com
New York State Open Data - Data depot for NYS agencies, some of the data is GIS ready.
Cornell University Geospatial Information Repository (CUGIR) - CUGIR is an active online data and metadata repository and a participating node in the National Spatial Data Infrastructure program.