I used to use a free software called task arrange for windows XP to rearrange my buttons in the taskbar. But the software does not work in Vista. I found another software named taskbar shuffle today that allows you to drag the buttons around in your taskbar.
On top of that, it comes with two new features. If you love how middle button clicks close firefox tabs, you can now do the same to close buttons in the taskbar. You can also now easily rearrange the icons in your system tray if you wish 🙂
Very awesome. I highly recommend it if you are looking for something similar.