Google Sites now provides a Mobile View (not editing) for smart-phones, mobile phones and other mobiles devices like iPhone and Android-based devices. The updates include: the horizontal navigation now works with touch screens; the sidebar can expand and collapse (pop-in and pop-out), which automatically collapses in portrait viewing mode and expands in landscape mode; and all the System Footer links, apart from "powered by Google Sites" disappear to give more vertical space and avoid wrapping.
These instructions tell you how you can enable the Mobile View (auto-rendering) for your Google Site.
If you want to edit a Google Site on an iPad then update your iPad to iOS5 and you can. For more information see the post I made exclusively on the iPad.
If your site contains items with a fixed width, a gadget, AdSense Ad or image wider than the screen size available this will appear wider than the display.
The mobile view only works on iOS or Android 2.2+ devices.
You can get this feature now on stand-alone/consumer/personal Google Sites and Google Apps domains with the Rapid Release track enabled.