I install and uninstall dozens of pieces of software weekly. I also (perhaps as a result of the first statement), rebuild my laptop from scratch about once every three of four months. So, it's a rare piece of software that lasts on my PC time after time. I thought I would highlight one of those today.
Taskbar Shuffle is a great little tool that lets you get drag-and-drop buttons on your taskbar. Simple and efficient. For that alone, it gets the honor of being re-installed everytime I rebuild my PC.
As an additional bonus, it supports a grouping feature that fixes something that I hate about the XP and Vista taskbar: grouping taskbar buttons from the same application together without ever collapsing them into the annoying "group menu."
It has a number of other features, including system tray reshuffling (but, I like to make everything on my system tray hidden, so this doesn't matter so much to me).
Go check it out. It's free. :)