Hanging or floorstanding?
Floor mount: Chief Mfg. had a product like this for plasma, but its not listed in the current catalog...Though there are models for conventional displays still in there.
Hanging: I've used Ergotron's 400 series, which has a gas spring to counterbalance the weight of the display.
[Link: ergotron.com] [Link: chiefmfg.com]jcmitch