So is it ok to use ferrite beads on speaker cables, interconnect cables, power cables, and cable wire? Anyone use them? I know I have them on my power cables now and I know that they are on some computer cables, but does anyone use them for home theater?

Thats a good question. I have a digital projector that came with component video cables with a ferrite clamp on one end. Does it clean the signal or block "noise"?
I also have one that came on a power cord for a Panasonic digital receiver. I've always wondered what the theory behind it all.

They are ferrite beads. They are inductors, chokes, that are tuned to block radio frequencies. They pass power line 60 or 50 Hz, but choke or resist higher the passage of higher frequencies. There function is to reduce RF interference that may be carried by a power line or signal cable. They come in different sizes for various cable diameters and there are versions for specific RF ranges. They work, they are harmless. They can be bought as after market snap on units to reduce interference problems.