Came across this handy website for WiFi users two weeks ago: JiWire. You can research all of the registered WiFi hotspots in your area or an area you might be going to. Enter the location in the search tool and you'll get a list — each listing has details on cost and a map of the location. There's even an AvantGo channel and WAP channel.
Hopefully this site will come in handy for WiFi travelers out there. :-)