I tried using an auto switching HDMI hub from Radio Shack, but even when the Apple TV was off, it still produced a black screen that prevented auto switching feature from working.
My solution at the time was to put the Apple TV on it's own TV HDMI, and manually switch to and from the input, while other devices such as an Xbox 360, bluray player, etc were connected to another HDMI input via the auto switch box. Powering those devices on made the switchbox activate that input.
I have now reworked my system, I purchased a harmony remote with a Chinese brand HDMI switchbox from Fry's electronic with a remote, the harmony now can control the switchbox without bothering with any auto switching feature.