Attached Link: http://www.joeashear.com/carrara/laser.mov

I decided to take a whack at this problem. The link above goes to my solution. If you want a beam of light to bounce off a mirror and illuminate whatever it hits, there's no practical way to do it with a regular light source. The caustics system could theoritically do it, but to get the level of precision you need it would probably take years to render the thing. In my solution the beams of light are just long thin rods. Each one has a glow color and a halo, and an Anything Glows object assigned to it. The reflected beam (the one that moves) is a child of the mirror object, so it pivots relative to the surface of the mirror, but at a different rate (it wouldn't make sense for it to always be pointing straight out of the mirror - it needs to vary depending on the angle of the mirror. The animation has just two keyframes, one at the halfway point and one at the end. The result isn't perfect - for one thing, the reflected laser beam would be visible if you were to peek behind the wall. Also, that beam should really be hidden when the mirror is facing toward the side, as in the first frame. But this works as a general proof-of-principle. The scene itself is at: http://www.joeashear.com/carrara/laser.car.zip - Joe