Since you live in a city that many people come to for vacation, maybe play tourist at home. I know that everywhere I have ever lived, there have been activities and places that I never got around to seeing. New York must be full of great and inexpensive activities that, as a resident working a full-time job, you don't normally get around to. Check out a new neighborhood, visit new parks or museums or restaurants, take a walking tour, attend a concert (might be some free ones in parks over the holiday weekend.) I'll bet you could find plenty of fun stuff to do over your long weekend.