I would suggest looking at the racing schedule at the top of this forum. The New England section will list the clubs active enough to hold events. The Barrington YC comes to mind as a very active fleet. They hold a regional every year and the occasional National. They also have frostbiting.
Contact John Fonseca at jcf123@comcast.net to find out about Sunfish racing in RI.
He is the New England Sunfish Class representative and should know of fleets that are not listed in the class schedule.
Barrington and Edgewood YCs (on opposite sides of Narragansett Bay) have active frostbiting fleets, I don't know about their other racing.