Disclaimer: I am in no way affiliated with this company. This is purely my opinion on a product that I think is cool that fits a certain niche that not many people know about.
I've wanted to get rid of my Sony SXRD rear projection behemoth of a TV and put a plasma on my wall in our living room. My problem is that our fireplace is quite tall and can only fit a 51" plasma and even then it’s pretty close to the ceiling. Having the TV that close to the ceiling is not great for comfort or viewing angle, so I refused to do it that way.
After a couple of years of looking for a reasonable option I came across the down and out mount from dynamic mounting. It allows you to mount a TV above your fireplace, or whatever, then grab the bottom of the tv and it swings out and drops down. It can move down pretty far and is now just above eye level. This way we can have it in the up position when we have company over, and pull it down when we are watching a movie or whatever.
The WAF (wife acceptance factor) is good, but not great. She says that the mount is "kinda ugly" when in the down position. Yea I guess it is, but when it's down pay attention to the TV...
The only downside IMO is the price. It isn't cheap but this was the only option for me. I think if you have the need its worth looking into.
http://i62.tinypic.com/6pajk1.jpg
http://i62.tinypic.com/idf046.jpg