I spent an evening last week helping NYCWireless install wifi in Brooklyn Bridge Park.
The process involved running a Covad DSL line from the basement of Smack Mellon, a nonprofit art organization, and setting up some additional equipment on the main floor, with antennae pointing out towards the park.
So now you can take your laptop over to Brooklyn Bridge Park and have wifi access. If your signal is weak, just move closer to Smack Mellon!
Related articles:
NYTimes: Deadline Set for Wireless Internet in Parks.