In fact, the NYC homebrewers' community is large and growing. There's even an organized group which has been growing by leaps and bounds. The New York City Homebrewers Guild
meets the third Thursday of every month, usually either at Burp Castle on 7th Street or Jimmy's the restaurant below Burp. Different topics every month, club-only contests, an annual contest that draws entries from around the country, all sorts of stuff. I recommend you pop down for our holiday party on December 21.
Edited to add: After years of having to mail-order/internet order or schlepping over 100 miles, we now have our very own LHBS. Brooklyn Homebrew
will cover just about anything you need, and if they don't have it they'll order it for you. Prices are mostly comparable to Northern Brewer's, cheaper considering shipping costs and everything is fresher.