Windows only: Preme is a Windows 7 shortcut utility that adds new and unique keyboard and mouse shortcuts, including a handful of useful ways to interact with windows using your mouse's scroll wheel.
For example, hold your mouse over any window's title bar and scroll down on your mouse wheel to minimise that window; middle-clicking the same title bar area (or just tapping the Escape key twice) will close the active window. The utility aims to be particularly user friendly, with screenshots and interactive demos designed to explain how each shortcut works, but in the end it's all a bit confusing. That said, the inventive shortcuts it adds are worth a look, particularly if you're big on mouse-based shortcuts.
Preme is a free download for Windows 7 only. What are your favourite Windows customisation tools? Let us know in the comments below.