Needs .NET 4 Framework.

Runs in the system tray. Add to Startup folder if you want it to
start with Windows.

Rotates using ctrl+alt+(arrow key).

Up is the default orientation.
Right is 90' clockwise.
Left is 90' counter-clockwise.
Down is 180'.

The mouse and arrow keys will rotate to match the screen. There's an option 
to disable either of these in the context menu.