If I'm running HDMI audio/video from my cable box then through my receiver to my Panny 50" Plasma, but some times I don't want to listen to TV using my receiver -- how can I just turn on the Plasma and get volume? Do I need to run another audio connection from the cable box to the Plasma like a left and right composite?

Thanks in advance.

If your plasma has a L/R composite analog audio input associated to that HDMI input, then running the L/R from the cable box to the plasma should work fine.

That's assuming your receiver can send an HDMI video signal to the plasma even when the receiver is turned off? If not, then just run a separate set of component video and L/R composite analog audio cables to the component input on the plasma.