High dynamic range displays. The latest prototype uses ultra-bright LEDs as the backlight for a LCD that acts as a transparency modulator. The resolution of the LEDs is far less than that of the LCD, so some software is needed to compensate with the LCD component.
Sony's "black" projection screen. It absorbs light that isn't a pure tone (ambient light), which is why it looks black when no image is projected. But primary colors (red, green and blue rays) are reflected, as shown on this explanatory diagram (via slashdot).
MEMS displays, presented in this video tour of MS Research. The idea is to use the regular chip manufacturing process to build chips with moving parts. You can have a chip that holds and orients many miniature mirrors. These cheap components can be combined in an large array and individually illuminated by small lasers to obtain a very large and cost-efficient display.
