Here’s a great video from Jonathan Stark, showing how you can turn a web app into a native iPhone app with the free tool PhoneGap. When combined with jQTouch, the jQuery plugin for mobile web development, you have a complete system for building native apps for various mobile platforms, all from html, css, and javascript.

PhoneGap supports iPhone, Android, Blackberry, Symbian, and Palm!

[youtube]http://www.youtube.com/watch?v=LcES5nIbMkk[/youtube]