I had my HD DVD player connected with 5.1 analog cables. When I got my Blu-ray player, I just moved those to that, and has connected my HD DVD player with a coaxial cable for now. I have a new receiver on it's way, so it's only temporary. But before I bought the receiver, I was thinking about getting some kind of switcher for the analog cables.
I have shared multiple analog 5.1 sources before, and used two A/V switches to do it. A bit of a PITA, and it looks like a kludge, although it worked fine.
But today, I placed an order for the Zektor 4 to 1 component switch, to be used for 5.1 analog audio duties. It should be much more user friendly, since it can be programmed to resond to any key on my universal remote.
Pricey to be sure, but it appears to be of very high quality.