Maybe I'm a bit odd, but I find it enjoyable to see what hosts are serving me up a web page. I used to actually go to Netcraft and look up sites I frequented out of curiosity. However, after seeing the Server Spy extension in a friend's screen shot, I found a much quicker way.

Server Spy is a Firefox extension that reads the headers of the web page being served to you and finds the web server being used. It then displays the result in the status bar, as is shown below. The screenshot below also demonstrates some of the fun of the extension. If a web server's home page isn't hosted by the web server in question… can you trust it?

When you click on the web server name, you get a dialog box that sometimes has more information. Depending on the site it may show the OS or Distro and features that the web server has enabled. Here we can see that Monkey's site uses PHP.

Server Spy isn't configurable or anything, but it does what it says and does it well. My only complaint is that sometimes going back and forwards in history will mess it up, but the fix is a simple reloading of the page.