There's a collection of shortcuts that do various actions in Windows. These are ones I've known and used. A full collection can be found at

All versions

Windows Key => Open the start menu

Windows Key + D => Minimize all windows and show the desktop (or restore it)

Windows Key + E => Open a new Windows Explorer window

Windows Key + F => Open a new Search window

Windows Key + L => Lock the computer

Windows Key + M => Minimize all

Windows Key + R => Open a run prompt

Windows Key + Pause/Break => Open the System properties window

Windows Key + Tab => Cycle through the applications along the task bar

Windows Key + Ctrl + Tab => Cycle through the quick start, desktop, and system tray.