The main Gay Pride event for the large and well-connected LGBT community throughout Long Island is Long Island Gay Pride, which comprises the 26th Annual Long Island Gay Pride Parade and Festival, held in the town of Huntington in mid-June. The date this year is June 11, 2016.
The the Long Island Pride Rally Parade & Festival in the Park takes place in the town of Huntington, which has direct service to Manhattan via Long Island Railroad (it's about a 70-minute train ride from NYC's Penn Station).
The Pride Parade begins at noon and runs south along Huntington's Park Avenue and then east along West Main Street to the site of the Long Island Pride Festival, Heckscher Park (at Main St. and Prime Ave.). The festival starts at 1 pm and is free of charge and lasts throughout the afternoon - there's entertainment, food vendors, a community fair, and kids' areas.Famed alternative rock band 10,000 Maniacs is headlining this year.
Note that it's just a 25-mile drive to Huntington from Sayville, home of the ferry service to the hugely popular gay resorts towns of Cherry Grove and the Pines on Fire Island. So if you're out on Fire Island at this time, consider heading over to Huntington for Pride.
Be sure to check out the travel site produced by the region's official tourism organization, the Long Island Convention & Visitors Bureau. The organization also produces a handy resource guide for same-sex couples looking for help planning gay weddings.