Just like the post subject says, the elegant Taskbar Shuffle makes it possible to rearrange items on your Windows taskbar, and by extension, makes it a LOT easier to be organized. New is version 2.0, which came out a few days ago and now works with groups (w00t!). And like some web browsers, you can also middle-click tabs to close them, which is a big boon if you're used to such behavior. What's more, you can also have new windows automatically get placed next to each other on the taskbar—see it and believe it!
One of those proverbial "They should include this as part of the operating system in the first place!" utilities.
Plus, works well on my vertically-stacked taskbar.
