Now that I understand better what FireSheep does, I agree - most of those plugins won't help. All but one. You can STILL use the "One Time Login" plugin, and it will project you from FireSheep - because it's only good for logging in one time. Even if firesheep hijacked your login authentication cookie - that login is only good for logging in ONE TIME. I agree as well, you should never login using your admin wordpress account over public wifi.