Lloyd's Java Shell is a java scripting tool (it could read and execute java-like statement from any input stream) that could easily be plugged into an application and modify its object - so it is also a configuration tool. It is also a good test tool, as you could easily use it to test any feature of your new object.
GSK is a portable framework for writing flexible servers and clients in C. It includes builtin support for HTTP, DNS, base 64, XML (which is mapped onto the object system), low-level network information (like ifconfig), efficient buffering, abstract socket I/O, and abstract datagram sockets. It also can use several different polling mechanisms: BSD's kqueue() and Solaris's /dev/poll, for efficiency, as well as select() and poll() for portability. It uses the GTK+ 1.2 object system, but it includes its own local copy, so GTK+ is not required. Glib is required.
Paranormal is an extremely customizable visualization plugin for XMMS, based (conceptually) on Winamp's AVS plugin. Its goal is to be as flexible as possible by providing a number of 'actuators' that perform various tasks involved in generating an image. These actuators can then be combined to create a nearly unlimited number of effects.
libclfll++ takes advantage of the abstract Library Load framework in the CoreLinux libclfw++ library by providing management of loading Linux shared libraries. Application developers define function objects as wrappers and can then dynamically load the functions. It is very useful for implementing a framework for plug-ins.
The deimos project provides some platform independent libraries which contain a reference memory allocator (garbage collector planned), virtual filesystem (Unix sockets, HTTP, etc), configfile management, and a clean build system (easy makefiles). These libs are used by DDS (Digital Disco System - mp3 player), vmOberon (oberon virtual machine), and ODMS (open document management system).