To make a single website installation, like the one you are visiting now, usable on multiple mobile devices such as iPhone, iPad, BlackBerry, netbooks, etcetera, I take the responsive approach, and use HTML5 and CSS3.
To see a demonstration of this responsive behavior, resize this browser screen. Or open this website on your handheld and see how the adaptive layout adjusts automatic to the screensize. Make sure you rotate between landscape and portrait mode, and see some magic*!
* Remember; this site is build on just one, single installation. Fancy something like this? Be bold.