He stripped down a 16" AOC USB-powered display, used a sheet of acrylic glass and made the necessary customizations to integrate the components into the side panel of his computer case.
All things considered, he says it's a relatively cheap and easy mod that delivers a kickass effect:
Joshua started the project with a 16" AOC USB-powered monitor that he stripped down to the LCD panel. He customized a sheet of acrylic to serve as the new side panel for his case, and cut out a hole for the display. The display needs considerable lighting behind it in order for its images to be visible, so he attached two LED strips to the side panel, and six more inside the case. The display's cable runs out of the back of the case. Windows sees the display as a third monitor, giving Joshua freedom to put just about whatever he likes on his side panel.
Via: The Tech Report