Appcelerator: Write Native iPhone, iPad, Android And Cross-Platform Desktop Apps Using JavaScript

Appcelerator has more than 19,000 developers using its tool to create cross-platform applications including mobile apps on iPhone and Android platform and iPad.

What is Appcelerator’s developer tool aimed at? Getting web developers to build first-rate native applications on all these platforms (it’s really a competitor of Adobe AIR). You can see demos of their current tool and API at http://www.appcelerator.com/