Did you know that middle-clicking (that is clicking on the mouse's middle button - usually the wheel) on a tab in most decent software applications will close the tab? Here's a small list of applications which honor this :

• Most main browsers (IE 7+, Opera 7.x+, Firefox 2.x+, Chrome 1.x+ - yes, Safari - doesn't)
• Visual Studio
• RSS Bandit (my RSS Reader of choice - have tried Google Reader and Feed Reader in the past but no thanks)

Why would this be useful? Because CTRL-F4 or searching for the "X" closing button might take more time and/or precision than middle clicking anywhere on the tab label up there :)