Mike, In Suffolk ,I think the best camp ground is Cedar point. It's out in East Hampton, on the Peconic bay side. Its by the water and this time of the year it wont be crowded......yet. The other options are :
Indian Island in Riverhead
Southhaven park........a lot of white trash camp there
Smithpoint Beach........Nice if you like to camp in parking lot by the ocean with Greyhound bus campers next to you.
Cathedral pines in Yapank
Wild wood in Wading River
A private campground in Greenport
Happy camping.