Headfirst at Baseball Heaven on Long Island early Aug - but sells out quickly
PG Northeast on June 3/4 in NJ
I can't paste the link on my iPad but you can google Blue Chip Prospects. They have showcases in NY, NJ and PA in June and July. I just looked and they don't have schools listed yet but they usually have a good list of northeast schools.
Diamond Nation in Flemington NJ will also have showcases this summer but I just googled and they aren't listed yet.
All Star Baseball Academy in PA has multiple prospect camps listed on their site with multiple locations and a good mix of 30 schools at all levels. (And I just noticed that NYdad also listed them). I don't have any experience with them but at first glance they look to be good events - if the schools they have listed are really showing up.
You can google specific areas and come up with showcases pretty much anywhere in NY, NJ and PA.