They are more common in the US than I think people realize as well. What type of equipment have you been using?

in the states it's almost exclusively rural area

i consulted them on biz and sales side so i don't remember their gear, but i remember both had quite a basic setup that worked pretty well. mind you, it was in urban areas (a 600k city in bolivia and a 2m city in serbia). serbian guys gone as far as building a file sharing network and setting up game servers

In the US I've had the most luck in fairly dense suburbs outside of major cities. If you get too rural it's hard to get the density where it needs to be to have decent profit margins. I honestly don't think there's any reason it couldn't work in urban areas in the US, just a different set of constraints. But it does seem to be less common.

Do you know of any just outside NYC, like in the NJ area?

I don't, sorry I'm mostly familiar with the western US. You might try this:

http://www.wispa.org/Directories/Find-a-WISP