libosl, the object storage layer, is a library for storing small to medium-sized data in relational tables. It is easy to use, lightweight, fast, and portable. libosl is suitable for applications that need only a small fraction of the features a full database management system provides.
AzureGE is a multi-platform OpenGL and OpenAL-based game engine. It has built-in support for I/O, threading, and networking, a particle system, a material generator, a texture generator, and a mesh/terrain generator. It is intended mainly for creating role playing games, but can also be used for other types of game.
Drumstick is a C++ wrapper around the ALSA library sequencer interface using Qt4 objects, idioms, and style. The ALSA sequencer provides software support for MIDI technology on Linux. Complementary multiplatform classes for SMF and WRK file processing are also included. This library is used in KMetronome, KMidimon, and KMid2 and was formerly known as "aseqmm".
junixsocket is a Java/JNI library that allows the use of Unix Domain Sockets (AF_UNIX sockets) from Java. In contrast to other implementations, junixsocket extends the Java Sockets API (java.net.Socket, java.net.SocketAddress, etc.) and even supports RMI over AF_UNIX. It is also possible to use it in conjunction with Connector/J to connect to a local MySQL server via Unix domain sockets.
NaturePHP is a classes wrapper using PHP's autoload to create a non-intrusive, simple, organized, and extensible library system. It is aimed at intermediate and advanced PHP developers, providing a lot of non-intrusive functionality for Web site and application development. Upcoming development will include internal library management and the ability to download/update libraries from the repository.