How would I mount an lcd tv over my masonry fireplace? The wall is plaster and the chimney is behind it...I doubt there are any studs back there but I'm not sure.
You can use masonry anchors for the mount, but there's probably no way to hide the wires in the wall
It might be easier to mount a piece of plywood using masonry anchors into the chimney, then mounting the lcd bracket to the plywood. Depending on how deep your plaster is, you may have to mount dimensional lumber to bring the plywood up flush.
I wouldn't put an lcd tv over a fireplace because:
Like kudzu9 said, theres lots of wires. In addition to the power line, any TV I would use would have a tivo box, a satellite box, a dvd player, an audio receiver, probably a couple game consoles. You might have a couple of those.
Also, I've found that I hate staring at TVs mounted much higher than eye level. I think I recall seeing a diagram somewhere that says screens should be mounted in a certain cone in front of the seating for viewing without excessive neck twisting.