Win+Home minimizes all programs except current the window.
Win+Pause/Break will open your system properties window. This can be helpful if you need to see the name of a computer or simple system statistics.
Ctrl+Shift+Esc will open the task manager.
Alt+Shift+Num lock opens the virtual mouse.
Win + Left : move application to left 50% of your screen.*
Win + Right : move application to right 50% of your screen.*
Win+Space to glance at your desktop.
Win+Shift+Left or Win+Shift+Right will send the current window to the other monitor.
Win + TAB = similar to Alt + TAB, but fancier.