sorry, but NYC is not a small town...
you really need to research what you
like and where you will be on what day,
then let us know your choices and we
can then help you narrow it down a bit.
just some of hundreds of online resource;
http://www.nycgo.com/ http://www.newyork.com/ http://www.nyctourist.com/ http://newyork.timeout.com/ http://newyork.citysearch.com/
If you like outdoors stuff and come in the Spring/Summer you might enjoy Governer's Island,
which just opened a few years ago to tourists, and gives you a nice boat ride and view of
Ellis & Liberty Islands which you can also go visit as well. accross the river in NJ is the newly
remodeled Liberty State Science Center. We now have a brand new Yankee Baseball Stadium.
Going to Coney Island and their Minor League team stadium is fun. Central Park is great too.
We now have a high-line park, which is a raised subway line that was converted to a Park,
very unique for NYC
http://www.thehighline.org/ also
http://www.chelseapiers.com/ can be fun.