Windows 7 has a few features that are new and different from the previous versions like XP and Vista. And here, the Windows key is coming into use more than what it was in the older versions.
Here are a few Windows 7 shortcut keys which mostly uses the Windows key to get things done -

Windows key with the arrows -
Windows + Left Arrow – Docks window to left side of the screen.
Windows + Right Arrow – Docks window to right side of the screen.
Windows + Up Arrow – Maximize the currently open window.
Windows + Down Arrow – Minimize the currently open window.

Along with the Shift key -
Windows + Shift + Left Arrow – Move the current window one monitor to the left.
Windows + Shift + Right Arrow – Move the current window one monitor to the right.

Mouse click included -
Ctrl + Left Click – Switch between the windows of that same program.
Shift + Left Click – Uses the taskbar item to open a new instance of a particular program.

Other -
Windows + Home key – Minimizes or maximizes the windows which are not active.
Windows + P – This enables the projector mode, and changes the external display settings. Useful while presenting something and connecting to a projector.
Windows + T – Jump to the taskbar to open a new window.

There might be many other shortcut keys, but these were what Mintywhite could find and share. Thanks to them.