jQTouch is a jQuery plugin for mobile web development on forward-thinking devices. You can create powerful mobile apps with just HTML, CSS, and jQuery. It supports native animations, automatic navigation, and themes for mobile WebKit browsers like iPhone, G1, and Pre.
jQTouch requires one basic theme to make page transitions work which is very small. One could use just the core CSS file to build a completely custom UI. Themes are additional CSS files which provide native-looking styles, mostly centered around the iPhone OS. Themes included are: Apple, jQT and Vanilla.