I am always looking for new ways of exploiting technology and pushing the boundaries online. Here is a little addon for Firefox I found this week that basically Hijacks a user's session over a non encrypted wi-fi connection. If a user is logged into Facebook, Twitter and many other social networks, you can capture the session and log into their account. It works in Windows XP and on the Mac, but I have yet to get it to work in Windows 7. You will need to install WinPcap as well.
You can download Firesheep. or read more about it here.
Recently a new addon came out to counter the Firesheep attack. Blacksheep alerts you if someone is using Firesheep on the wi-fi network you are connected to. The other way to prevent it is to make sure you are always using a secure network and logging out of your sessions when not in use. You can read about & download Blacksheep here.