I highly recomend Captain Jeff Becker out of Oreint Point NY. He fishes the North Fork of Long Island worth the trip out there, about 2hrs from NYC.He also can recomend some one if you want to fish closer to NYC but the striper fishing will be better on the North Fork that time of year.
JT, I second the Urban Angler recommendation. Take the 4 or the 5 to Union Square and from there you can walk about 5 minutes to the shop. There are other subway lines as well that will drop you off close by.
Also keep in mind that fishing for striped bass in the summer will most likely happen in the middle of the night.