ImLab is a free open source graphical application for Scientific Image Processing that runs in Windows, Linux and many other UNIX systems. It supports multiple windows, data types including 32 bit integers, 32 bit real numbers and complex numbers.
GLIP-Lib is an OpenGL image processing library written in C++. It features all the necessary tools to quickly build texture filters and pipelines and operate them on the GPU.
kradview is a viewer of images obtained for some different sources: X-ray, NMR and all DICOM-compatible imaging devices. Its aim is to be a complete platform for medical imaging and image processing.