darktable is an open source photography workflow application
Lynkeos is an astronomical webcam image processing software for OS X.
ProStack - a platform for image processing and analysis
Graphic Live Mixer
Tools to train Image Operators automatically from a set of samples.
Advanced image processing toolbox for Scilab on Unix/Linux/Mac OS
Bildster is an image processing library for educational purposes.
A Library for Interactive Modelling and Visualisation
Python-accessible toolkit for Geoscience & Remote Sensing Applications