A user interface convention that is emerging as a standard for applications that support having multiple pages or documents open in tabs, such as web browsers (including Firefox, Internet Explorer 7, and Opera 9) and IDEs (including Visual Studio and, in an upcoming version, Eclipse), is the ability to click a tab with the middle mouse button to close the tab. This is useful for several reasons: (1) It's easier to position the mouse cursor over a tab than on a small button on the tab; (2) it prevents accidental closing of a tab with the left mouse button (when the close button on the tab is left-clicked inadvertently instead of on the remainder of the tab area); and (3) optionally, it allows the close button each tab to be removed (resulting in more available space on the tab for displaying the name of the tab's document).
I always thought it would be nice to be able to apply this same UI convention to Windows Taskbar buttons. After all, what is the Windows Taskbar but a tabbed view of all open applications? The ability to middle-click a Taskbar button to close it would be much nicer than having to right-click an application's Taskbar button and choose "Close" from the context menu that appears. (Trying to close many applications in quick succession in this way can be particularly aggravating when closing an application that doesn't follow the common convention of having the "Close" option as the bottom option in the context menu, such as cmd.exe command prompt windows – you end up having to hunt for the "Close" option among the other options, instead of just clicking the "Close" option immediately.)
I recently came across a free utility that allows a middle-click on a Taskbar button to close the application: Taskbar Shuffle by Jay E. The primary purpose of Taskbar Shuffle is, as its name implies, to allow Taskbar buttons to be reordered via a simple drag-drop. However, Taskbar Shuffle does also implement the middle-click-to-close functionality. Very cool!
I was initially a bit leery of installing a utility that hooks directly into Windows' explorer.exe (as I presume that Taskbar Shuffle must do in order to provide the functionality that it does), for fear that the utility could potentially bring down Explorer itself if something were to go wrong. However, I searched around for comments on the application, and found many very positive comments (including on the app's own forum) about the app, and no negative comments, so I took the plunge and installed it. I'm glad I did; on my machine (running 32-bit Windows XP Pro), Taskbar Shuffle is rock-solid stable! I've found it to be one of those extension-type applications that is just so useful, you wonder why its functionality isn't built into the base product itself (in this case, Windows).
One caveat: Apparently the current version (v2.2 as of this writing) doesn't support 64-bit versions of Windows yet. A 64-bit version might be on the way, though; the application appears to be actively developed, and some text near the download link notes "hold tight for 64-bit".
Update 7/1/2009: A 64-bit version is now available! Go check it out.
Go get Taskbar Shuffle from Jay E.'s website, here.