Know the Windows key in Windows 7

Windows Key + Left Key     = To dock the current Window left
Windows Key + Right Key  = To dock the current Window right
Windows Key + Up Key      = Maximize the current window
Windows Key + Down Key = Minimize the current window
Windows Key + L                = To lock your desktop/computer
Windows Key + Tab            = Cycles through open windows
Windows Key + Spacebar   = Makes all windows transparent


Update:  I forgot to include this very handy one:
Windows Key + D    = Minimize/Restore all open Windows