The latest issue of Mother Earth News mentions that the East River in New York City is the site of a new tidal power turbine installation (six turbines installed Sept. '04 by Verdant Power). It supplies power for about 200 homes. This is apparently part of a 10 MW project that will eventually include 300 turbines.
More info here:
http://www.verdantpower.com/Initiatives/eastriver.shtml