The Fairfield, CT 1/2 is June 28, http://www.fairfieldhalf.org/index.htm.  It is a scenic but challenging course that finishes on the beach and is accessible by MetroNorth (a little over an hour on the train and the station is about 1.5 miles from the start).  I've done this race 3-4 times in the past, taking MetroNorth once.

A little later in the season is the New Haven 20K, http://www.newhavenroadrace.org/.  Also accessible by MetroNorth.