I'm not sure why, but recently an increasing number of people are coming to this site to find maps of New York. So, here are my favorites:
Subway map - Click on any portion and it will zoom in
Google map - Type in "New York, NY" or a zipcode (10022 is midtown east) or a neighborhood ("Greenwich Village, New York, NY) and press enter; and you can navigate up and down from there. The real fun is then entering something you're looking for - a business ("Starbucks") or a kind of business ("coffee shop") - and then clicking "Find Businesses." NY is huge, so it's not complete, but it can almost always find you something useful.
Manhattan Neighborhoods - if you're not sure where a neighborhood is, this will give you a general idea.
Manhattan Neighborhoods - A second choice because it's got so much detail, it's sometimes hard to read.
Enjoy your trip!