Photodon monitor hoods mentioned in Photo Techniques Magazine Sept/Oct 2003,
article "Calibrating the Digital Darkroom"
The viewing environment
Once the monitor is calibrated and an image brought into the corrected color space, adjustments can be made. For the best results, set up your monitor in a room with minimal ambient light and no windows (or, at the least, have tightly closed blinds).

Figure 1 shows the main monitor with a hood. (This one was purchased from www.photodon.com.) A hood is no longer a luxury, but instead a necessity—much like a lens shade on a lens. Lighting in a studio setting usually is fluorescent ceiling fixtures that cast a greenish glare across the front of the monitor. Where the studio is near a window, daylight glare also affects the screen. If you have a smaller light in your workspace, move it to the side of the monitor, not directly in front or behind it. A monitor hood (starting at $18) helps block glare, creating a significant viewing improvement. Without the glare, color decisions are easier and eye strain is reduced. LCD monitors and flat screen CRT monitors also help to reduce glare reflection, and wearing darker clothes helps reduce your own reflection.

"Calibrating the Digital Darkroom entire article"