make sure to see the empire state building at night. at the top, the view of the city is amazing. i believe it's open until midnight, and i think tickets are ~$12 (haven't been there in a while).
virgil's bbq is a big nyc restaurant that everyone goes to if you're into roasted meats (43rd or 44th near the subway station). take a trip to chinatown and grab a box of the $1 mei fun that is sold in carts along canal street. restaurants like harmony palace and the big wong are notable, but i think the food is pretty good everywhere in chinatown. also, you can get nice roast pork or curry chicken buns at the bakeries there. and bubble tea. if you like indian food, 1st avenue and 7th street has a lot of colorfully-lit cheap eats. i'm particular for "rupali". people will try to usher you into other restaurants in that cluster so look for the rupali sign or there's no escape!
soho's a nice place to run around if your cash is burning a hole in your pocket. or nice to see designer clothing. but if clothing's not your game...
wall street is cool. the new york stock exchange doesn't allow visitors anymore, but other sights like federal hall and the south street seaport are worth a trip for some great photos. the seaport also has nice places to get a drink and relax, and i believe it's the summer time festival down there so there will probably be acts and live music and such. a really nice place.
i'm content to see sights on foot. walking around the upper east and west sides near central park is fun and the numerous embassies and other fabulous housing establishments provide plenty of eye candy. i also enjoy the east and west villages. east village has cool punk rock and japanese kids, and you can fill your need for latex on st. marks. also cheap sushi and fun free clubs/hang-outs like lit (2nd ave and 7th st.?) on saturdays and rafifis (1st ave and 13th street) on fridays where 80's, pop, rock etc. is played. the pyramid is a legendary club in the area. and if you want to check out a venue legend, cbgb's on bowery has some acts that are worth the few bucks for the enjoyment and the beer. west village is full of nice cafes and... latex (a village thing?). no really, it's really a beautiful place.
see rockefeller center too.
oh and if you're in ny, see the yankees play!
geez can't think of anything else right now b/c my headaches. hope you have a great time!