I am going to be in New York for about 3 weeks from end Aug to mid September. I have not been there for years, so I wonder what I could see, which is ideally a bit (but not too much) off the beaten track.
On Broadway, there are a couple of shows I have heard good things about, Kinky Boots is one. Getting a ticket would be difficult? What about the US Open…IIRC its in Queens? Would it even be advisable? I have had some bad experiences at Wimbledon, with the crowds and facilities.
Katz’s Deli, pastrami sandwich. Directly from the airport, if possible.
Go see The Colbert Show. There’s a line, so get there early.
Colbert tapings are fun, but it’s hard to get tickets. They’re booked up for months ahead of time. You will probably have better luck with Broadway shows. For most of them it’s not that hard to get tickets for performances in a few weeks and there are also options for getting tickets the day of the performance.
The U.S. Open is a great experience, and yes, it’s in Flushing, Queens. It’s crowded and the food (while good) is expensive, but I go every year. It can be very affordable if you go to an early date in the tournament and get a grounds pass instead of going to the big stadium, and wandering from court to court is a lot of fun.
The thing to do with Colbert is to keep checking back on the website for cancellations, which happen all the time. We got tickets the day before the taping that way. Also, stop at an REI and pick up one of those three-legged camp chairs for $20. Unless you like sitting on concrete or standing for 2-3 hours. They won’t take them away from you at the door, either.
You could look really suspicious and have a NYC cop do a stop and frisk – but only if you aren’t carrying something you shouldn’t. If you have someone going with you you could have them record it, or at least get a picture suitable for framing. 
As tacky tourist as it sounds, if you make your way to lower Manhattan, take the Staten Island Ferry.
Plenty of free concerts in parks during that time.
You know for after you are bored with the museums and such.
Yes, the Staten Island Ferry is a nice ride and it’s cheap.
The Statue of Liberty: If you’re at the bottom of Manhattan as you’d be if you do the Staten Island Ferry, you’ll be near the ferry to Liberty Island. You might want to check on this, as I may not be current, but when I was there last, the Immigration Museum was in the pedestal of the statue. It had been moved from Ellis Island because Ellis was closed. Even if it’s open, you do NOT want to climb up the Statue to look out of the windows in her crown. It’s a long spiral stairway going up with someone’s rear end in front of you at the same level as your face. There’s some maneuvering around at the windows and the view isn’t all that wonderful, and then it’s another spiral staircase down. Though I guess you could knee the back of the head of the person in front of you if you’re into vengeance.
I was stationed in NYC for 2 1/2 years. One thing I regret is never taking the tour boat that goes up the Hudson River to West Point and returns. It could be the Circle Line. There’s another tour that goes around Manhattan. I don’t miss not doing that. You’d enjoy that more if it’s a cooler day. Mid 70s or less. Bring a sweater or jacket with you. But the ride might not be much fun if it’s in the 80s or 90s.
Don’t get sucked into a 3 card monte game. You won’t win.
I loved Greenwich Village but I haven’t been there in decades. Even when I worked near Madison Square I rarely ventured past Union Square. However there are somethings that probably don’t change.
There are some wonderful walking tours you should check out. The village has some incredible history that you can’t appreciate from the road. As I recall, most start from Washington Square.
The music scene there is vibrant, from jazz to cutting edge alternative. The Village Voice is probably still the best source for that it looks like they still have a print edition. Also lots of art cinema. But both are true for the whole city. You should definitely go to at least one concert at Avery Fischer hall and Lincoln Center.
I agree that the US Open is a really fun time, whether you spend the big bucks, or go bargain with the field pass.
Governors Island is now open as a park/historical site, it’s awesome.
Depending on what you’re into…
The Cathedral of St. John the Divine.
The Intrepid Air-Space museum (one of the space shuttles lives there)
American Sign Language poetry-comedy Slam, first friday of every month
The Strand used bookstore
Saturday Greenmarket at Union Square
Brooklyn Botanic Gardens
Pizza at: (choose one) Lombardi’s (Manhattan), DiFara’s (Brooklyn), Nick’s (Queens)
Panorama of the City of New York (walking distance from the Open)
The Cyclone (rollercoaster) and the Cyclones (minor league baseball)
“Little Odessa” the Russian immigrant neighborhood in Brighton Beach.
Spa Castle - 4 story Korean bathspa (weekdays better than weekends)
At that time of year there’s about a 50/50 chance the weather will be hot and humid beyond description or just lovely and perfect, so plan accordingly.
In honor of its 100th anniversary, The Woolworth Building is offering limited tours of its lobby. $10 for a 15 minute tour or $30 for a guided tour of the lobby and the outside. I snagged a ticket for October and I’m pretty psyched. You need to book them in advance at http://woolworthtours.com/
Kinky Boots shouldn’t be too hard to get tickets for but I think it does sell out so you’d want to book your ticket in advance (like start looking now). It was good but I liked Matilda better. Book of Mormon was best but your chances of getting a ticket this late are slim.
That sounds cool. There used to be a books store there that specialized in very hard to find law books and study aids. I wouldn’t have made it through w/o that book store but the elevators there used to scare the shit out of me. 
You should be able to get Yankees and/or Mets tickets pretty cheap this September. 
Thanks to everyone who gave their kind suggestions. I visited many of the place mentioned.
Specifically
Intrepid was awesome. The US open was a great experience. The Circle Line cruise is worth it’s weight in gold. The Met , MOMA and Lincoln Center were worth it as well. I’ll admit Broadway was a bit underwhelming.
Also went upstate. Hudson Valley is some of the most beautiful country I have ever seen.
Long live the dope!