There's nothing quite like celebrating the Fourth of July in New York City. There's so much to do and the Macy's Fireworks show is so notorious that a lot of the country sits to watch it on television. Going in person, you'll encounter a large crowd but its definitely worth it becuase viewing it on TV isn't anything like viewing in person. Its one of those things you have to do once.
Roosevelt Island Tram Station (Manhattan Side)
Take a Ride on the Tram and visit Roosevelt ISland. There's a great farmers' market there on Saturdays.