Take a peek at Time Out New York magazine.
If you're in for a long weekend, all of the touristy things will be right in the Rockefeller Plaza/Times Square area. Go to the Top of the Rock or the Empire State. Hit FAO Shwartz, The M&M Store. Go to St. Patrick's.
Don't be shy about going to the outer boroughs for dinner. Astoria is awesome for Greek (Stamatis - YUMMM!!!) and Asian food. Brooklyn Heights has an amazing view of the skyline plus great food.
If you head downtown, do some shopping in SOHO and grab lunch in Chinatown (don't be afraid - Use YELP and you'll find a good one). Lots of fun shopping there, too. Visit the 9/11 memorial if you are up to it (I haven't felt up to it yet).
NYC will be a MADHOUSE over the next few weeks but it's a magical madhouse.
One other fun thing is to walk down 47th street between 6th and 7th - the Diamond District! So much fun.
Also, look up John's Pizza on West 44th (Pizza in an old converted church) and then stop by Schmackary's for cookies on 45th. YUM!!!
And of course, go see a play. Don't shy away from off-Broadway plays. They are awesome as well. Just not as elaborate. Cabaret is my all time favorite. Very adult and deep and so entertaining. Try to get tickets.
I could go on and on and on! Have fun!!!!