Most Android applications are built using Google’s official Android SDK, though there are dozens of other cross-platform mobile development frameworks that make it easier to build once and deploy on multiple operating systems. jQuery Mobile, Titanium (generates nativa Java code), Adobe PhoneGap, and Sencha Touch are the most popular HTML, CSS, and javascript-based frameworks, aimed at Web developers. Xamarin (C#), MoSync (C++), and RhoMobile (Ruby) were built for developers with knowledge of specific programming languages. There are also several frameworks aimed at game developers: Corona SDK, Flixel, Unity3D, etc. Discuss all of these here.
http://forum.xda-developers.com/tools/frameworks