Tux Paint is a simple and entertaining drawing program geared towards young children. It has a simple interface, sound effects, and a cartoon character (Tux, the Linux penguin). Along with drawing brush strokes, lines and shapes, you can also enter text and place "rubber stamp" (or "sticker") images on the picture. Tux Paint is extensible, and could be useful in an educational environment (such as a grammar, elementary, or grade school). It's portable across numerous platforms, and runs well even on slower systems like the Pentium 133MHz.
SIP provides image processing, pattern recognition, and computer vision routines for SciLab, a Matlab-like matrix-oriented programming environment. SIP is able to read/write images in almost 90 major formats, including JPEG, PNG, BMP, GIF, FITS, and TIFF. It includes routines for filtering, segmentation, edge detection, morphology, curvature, fractal dimension, distance transforms, multiscale skeletons, and more.
FrAid (Fr[actal] Aid) is a programming language that is appropriate for mathematical computations, visualization, batch processing, and more. It features both a standalone application that provides a programming environment for the language and a system for integrating the language with Java. The Java interface allows mathematical equations and formulas to be used with Java code, making it easier to process numerical computations, symbolic computations, imaging, CAD, and more.
MapMemo allows you to drag your files onto any graphic (map, photo, scan, illustration, screenshot, etc.), and thus give them a visual, location-based relation. It uses only aliases of your files which, when you click on an appropriate location, will open in their original application. You can use layers, info windows, colors, and comment fields to organize your files on the map.
SAGA GIS (System for Automated Geo-scientific Analysis) is a geographical information system (GIS). The SAGA GIS API supports grid data like digital terrain models and satellite images, vector data, and tables. This API makes it easy to implement new algorithms and exempts the developer from hassle programming overhead like user-interface design or file I/O. SAGA GIS comes with a large collection of modules, in areas of terrain-analysis, geo-statistics, image processing, and process simulation.