Magnifier is a freeware Virtual Magnifying Glass software for Windows & Linux that allows you to enlarge any portion of your desktop screen. Once installed, you can launch the application using the shortcut. Once launched, the program shows a magnifying glass lens that follows the mouse movement. You can move the lens around the screen to view magnification of any screen area. To close the lens, click the left mouse button. It also supports multi-monitor display systems.

Other key features include:

-Dynamic Mode (in Beta): Allows users to magnify and interact with the window under the magnifier (such as mouse, scroll wheel, keyboard, etc…)
-Invert colors
-Show the center pixel’s RGB values, in both decimal and hexadecimal.
-Multi-monitor support
-Lens height and width can have any size
-Mouse scroll-wheel now controls zoom factor
-Hotkey shows/hides the magnifier (currently hardcoded to CTRL-ALT-e)

Download Virtual Magnifying Glass for Windows here and for Linux here