Libslack is a library of general utilities designed to make UNIX/C programming a bit easier on the eye. It was originally implemented as part of the daemon program. It's a small library with lots of functionality, is accurately documented and was thoroughly tested. Good library naming conventions are not rigorously observed on the principle that common operations should always be easy to write and code should always be easy to read.
LibStroke is a stroke and gesture recognition library. It can be used to easily add the capability to recognize mouse strokes to an application. Examples of programs which are LibStroke-enabled are FVWM2, gEDA, and PCB. There are GNOME, C, TCL, and Java libraries and bindings available aswell.
libxmi is a standalone C library for rasterizing 2-D vector graphics primitives such as wide polygonal lines, circular and elliptic arcs, and filled polygons. It's based on the vector graphics code in most X Window System servers. Some rendering extensions have been added, such as support for multicolored dashing patterns. Despite its origins, libxmi is completely decoupled from X11. It draws vector graphics onto a user-supplied matrix of pixels, not onto an on-screen window. It uses its own two-stage graphics pipeline.
Licq includes all the basic features of ICQ, like sending/receiving messages, chat, file transfer, contact list with pixmaps and user status, basic/extended user info, adding/editing users from within the GUI, user history, user groups, and new user registration. All commands and information are available through a simple and convenient tab dialog. Licq also has a completely configurable user interface with Skin and Icon pack support. It is written in C++ and comes with a GUI plugin using the Qt widget set. Other plugins are also available, like basic MSN support.