Real-time tidal data:

NOAA National Water Level Observation Network (NWLON)

Corps of Engineers

USGS Tide Guages - USGS gauges can be accessed via nowCOAST. Select northeast, river, gage height, and realtime to select all of the USGS stream gages. Some of the downstream gages are tide gages. Estuary gauges on Long Island and the Hudson River are found here.