Repeat after me: I will not use unsecured wireless access points, I will not use unsecured wireless access points, I will not use unsecured wireless access points…
Among the websites whose cookies Firesheep can identify are Facebook, Flickr, Amazon.com, bit.ly, Google, Twitter, Yahoo, WordPress, and many others.
Firefox extension makes social network ID spoofing trivial
Note that all this requires is the installation of WinPCAP and the extension. And no, I will not add links to make it easier for you to find this.