Almond Java Application Framework is an easy to use Swing based framework for Java applications. Almond is very much inspired by the K Desktop Environment.
Mobile.Windows.Forms offers functionality for developing mobile applications using .NET Compact Framework 1.0, including multiple screen configurations, keyboard navigation and XML based user interface definitions.
The Simple Object-Oriented Game Library is basically a simplification of SDL with some nifty features. SOOGL is used in a C++ course at Mälardalen University (http://www.mdh.se) and is mainly intended for beginners.
A C# framework used to simplify the development of larger applications in .Net.