This is what I use...
Philips USA - PH-61153 - 4 x 1 Automatic Selection S-Video/Audio Selector and RF Modulator
I picked up two of them in Walmart for 22.99 apiece, and they perform flawlessly. They're powered, so there is no (noticable)signal loss...and they automatically select the input that's turned on. No more flipping switches.
I cheated a little bit, and used the second one as a component input selector (my 360, PS3, and DVD audio are either optical or coaxial...don't need the rca connections). Works like a freaking charm.