TunnelVision allows you to hide the parts of the screen where your mouse cursor is not, effectively increasing privacy (though at a cost).

Features:

• configurable viewport shape, size
• configurable color
• configurable background image (with tiling, scale, centered modes)
• tiny program, low memory footprint (when no background image is used)
• supports Windows 95 and later (though tested more extensively on 2000+)
• lovely GPL license!