I love this kind of thread.
A great way of finding hotspots for those of you with cars is wardriving (google it). You can do it with a normal PCMCIA card, but its best to crack one open and solder a bigger aerial onto the board, instructions are on google. here's a shabby one I made earlier, the aerial's magnetic and sticks to the roof of my car. Sorry for the tape obscuring the interesting bits.:
Then all you need is a program like Netstumbler (windows) from
http://stumbler.net or Kismet (linux) from either
http://www.kismetwireless.net/ or just 'sudo apt-get install kismet' if you use ubuntu/debian . Drive round and watch in amazement as you find upwards of 100 APs per drive. I find that around 80% are not WEPed. If you use a backpack, it would be possible to do this on a bike.