Light-Weight Visual Components Library (LwVCL) is a powerful, small, fast, efficient, framework of visual components that provides a rich set of customizable, flexible user interface components. There are versions for J2SE/J2ME Personal Profile, J2ME MIDP, .NET, and SWT. This provides a unified GUI framework for different platforms that provides the same API, the same concepts, and the same look and feel.
MUSCLE (Multi User Server Client Linking Environment) is an N-way messaging server and networking API. It includes client-side networking APIs for various languages, including C, C++, C#, Delphi, Java, and Python. MUSCLE lets programs communicate over a network via streams of serialized Message objects. The included server program ("muscled") lets its clients message each other and store information in its server-side hierarchical database. The database supports flexible queries via hierarchical wildcarding, and "live" updates via a subscription mechanism.
PhysicsFS is a library to provide abstract access to various archives. The programmer defines a "write directory" on the physical filesystem. No file writing done through the PhysicsFS API can leave that write directory, for security. For file reading, the programmer lists directories and archives that form a "search path". Once the search path is defined, it becomes a single, transparent, hierarchical filesystem. This makes for easy access to ZIP files in the same way as you access a file directly on the disk, and it makes it easy to ship a new archive that will override a previous archive on a per-file basis. Symbolic links can be disabled, for added safety. Finally, PhysicsFS gives you a platform- abstracted means to determine if CD-ROMs are available, the user's home directory, where in the real filesystem your program is running, etc.