Titanium from Appcelerator is an open source platform for building Rich Internet Applications (RIAs) with web technology. As a concept it's nothing new, there are numerous commercial and open source competitors, including Adobe's AIR product. But two important differences set Titanium apart from the crowd.
Firstly, it enables developers to create native look-and-feel desktop and mobile applications using only open standard web languages. This means web-savvy developers can start creating applications immediately - without having to learn additional languages such as Java and Objective C, along with their extensive language-specific libraries and APIs.
Secondly, Titanium can take a single development project and build executable packages for any supported desktop or mobile platform. Application package targets already include Windows, Mac OS X and Linux desktops, together with Android smartphones/tablets and Apple's iOS iPhone/iPad devices and Blackberry devices.
The flexibility of a cross-platform solution, where you write the code only once, then deploy it to multiple platforms is very attractive.