Verdant Power has gotten approval to install 30 underwater turbines in the East River and hook them up to the grid, generating 1 MW. Currently, they have six test turbines. Extensve testing has shown that fish are not harmed by the turbines.
Tidal power like this can be installed close to where the power will be used and is also completely predictable as to when the electicity will be generated.
Links. CS Monitor, EcoGeek.