I would recommend iUI, which is based on the code originally developed by Joe Hewitt - the creator of Firebug.<p>I have developed a pretty advanced iPhone webapp with it (online food diary searching while you type). The only thing was that I had to disable page transitioning emulating sliding screens, as the animation was quite slow and unpleasant.<p>Since then, Apple added support for proprietary CSS extensions providing access to "native" animations, but due to the availability of native SDK, I don't think it is widely used and on a first glance this is not supported in iUI.<p>For reading and reference I would recommend Apple's Developer Connection topic <a href="http://developer.apple.com/safari/library/referencelibrary/GettingStarted/GS_iPhoneWebApp/index.html" rel="nofollow">http://developer.apple.com/safari/library/referencelibrary/G...</a>, which provides several "entry" points to documentation, guides, and samples. Still, for development it makes a lot of sense to save efforts and build on top of an existing library, such as iUI, which provides you the app structure, pre-built JavaScript for iPhone-specific manipulations, and images.<p>I would be careful with iWebKit since it seems to use GPL, which may result in issues with non-open source use.