RhoMobile!

PhoneGap is an open source development tool for building iPhone, Android, Blackberry and other mobile apps with JavaScript.

Apache Cordova is a set of device APIs that allow a mobile app developer to access native device function such as the camera or accelerometer from JavaScript. Combined with a UI framework such as jQuery Mobile or Dojo Mobile or Sencha Touch, this allows a smartphone app to be developed with just HTML, CSS, and JavaScript.

Haskell is an advanced purely-functional programming language. An open-source product of more than twenty years of cutting-edge research, it allows rapid development of robust, concise, correct software. With strong support for integration with other languages, built-in concurrency and parallelism, debuggers, profilers and rich libraries.

Type intelligentlyWorld-class code completion unlocks the iOS, Android, and OS X APIs. Quickly look up methods and types, and discover API functionality.

With Adobe AIR, developers can use proven tools to build rich Internet applications (RIAs) that deploy to the desktop. Try it today.

Appcelerator Titanium, offered for free by Appcelerator, lets web developers use web technologies, open source and cloud computing to build native apps for iPhone, Android, Windows, Mac OSX and Linux.

WebDGap allows you to convert any website or HTML/CSS/JavaScript web application to a native Windows, Mac, Linux, and Chrome application.

Elixir is a dynamic, functional language designed for building scalable and maintainable applications.

Rapid Application Development tools for native Android, iOS and desktop applications. The simple way to quickly program real world apps. Programming language similar to Visual Basic.

Convertigo is the most advanced Open Source Mobile Application Development Platform for Enterprises, featuring all the required components needed to develop and to run cross-platform mobile enterprises application connected to enterprise's back-end business applications.

Corona has become one of the world's most advanced mobile app development tools.

Codename One provides a comprehensive solution for WORA (write-once-run-anywhere) mobile app development. You write the applications in Java using and deploy the application to Android, iOS, Windows Phone, or other platforms. The resulting app is a native app (not HTML5).

Sencha Touch allows you to develop mobile web apps that look and feel native on iPhone, Android, and BlackBerry touch devices.Free & open source license available for open source projects.

Kurogo is open-source Mobile Optimized Middleware™ from Modo Labs that connects content from a wide range of back-end sources, refactors and recombines it, and makes it available on any mobile device.