Mobile development platform for javascript developers: Appcelerator Titanium lets you use web technologies, open source and cloud computing to build native apps for iPhone, Android, Windows, Mac OSX and Linux.
PhoneGap is an open source development framework for building cross-platform mobile apps. Build apps in HTML and JavaScript and still take advantage of core features in iPhone/iTouch, iPad, Google Android, Palm, Symbian and Blackberry SDKs.