libTISCH is a framework for easy development of multi-touch applications. It contains tools for video processing, calibration, gesture recognition and, most importantly, a GUI toolkit with widgets that utilize the multi-touch gestures detected by the lower layers. It runs on Linux, Mac OS X, and Windows.
liberror is a library for C and C++ that addresses the allegedly simply task of printing messages. It is essentially a feature-rich substitute for fprintf. Features include colours via ANSI mark-up, multiple error streams, report files, automatic error number assignment, filtering by number, subsystems, and groups, buffering with manual filtering and re-issuing, callbacks, error counters, time stamping, and message styles.
PageLayout is a layout lanager for Java Swing/AWT that encapsulates, in a single library, the functionality of many other layout managers. It allows you to lay out components in appropriately aligned rows, columns, and grids. The elements of rows, columns, and grids may themselves be rows, columns, and grids of components. As a result, relatively complex layouts can be managed with code that is compact and conceptually quite straightforward to understand and, therefore, maintain.
reacTIVision is a computer vision framework for the fast and robust tracking of fiducial markers attached to physical objects, as well as for multi-touch finger tracking. It was mainly designed as a toolkit for the rapid development of table-based tangible user interfaces and interactive multi-touch surfaces such as the reacTable. Client application examples are available for various programming environments such as C++, Java, C#, Processing, PureData, Max/MSP, and Quartz Composer.
wxOptParse is a Python program that brings up a graphical representation of the command line options of a Python program, if it happens to use the standard optparse module. What this means is that if if you have a program that uses optparse you can optionally click on checkboxes, edit boxes, combo boxes, etc. instead of using the command line.