Probably everyone knows a few shortcut keys in Windows and various applications. Ctrl-C and Ctrl-V being one of the most popular, I guesss. But there are really a lot of very useful shortcut keys introduced in Windows 7.
I am myself a keyboard freak: I like doing many things from the keyboard. In fact, I try to avoid the mouse as much as possible. Because I code and write, my hands are usually on the keyboard, so moving onto the mouse takes away precious typing time
The following applies to Windows 7 only.
Did you know you can maximize (Win+Up) and restore/minimize (Win+Down, although this only restores if the window is maximized) windows easily, or even move a maximized window from one monitor to the other (Win+Shift+Left or Win+Shift+Right, based on the direction you are moving)? I also like the fill left or fill right side shortcuts (Win+Left, Win+Right). Arranging windows was never quite so easy.
It takes a moment of time to learn a few shortcuts, but I find that it speeds up everyday operations so much.
You will find a list of shortcuts here:
New Keyboard shortcut keys (hotkeys) in Windows 7
Or if you really feel like learning, here is a more complete list:
Windows 7 keyboard shorcuts
Update 27.10.2009 - Another page with useful information on shortcuts for Windows 7: The Master Lift of new Windows 7 shortcuts