Image Precessing: Algorithms - Links to many different image processing algorithms - http://www.efg2.com/Lab/Library/ImageProcessing/Algorithms.htm
ImLib3D - ImLib3D is an open source C++ library for 3D (volumetric) image processing. It comes with an optional viewer that features multiplanar views, animations, vector field views and 3D (OpenGL) multiplanar. - http://imlib3d.sourceforge.net
IC Imaging Control -- image acquisition ActiveX - IC Imaging Control is an image acquisition SDK that works with any video source compiling to Microsoft's WDM specification. As an ActiveX and C++ Class Library, IC Imaging Control allows programmers to create image acquisition applications with only a few - http://www.imagingcontrol.com/
Software List - List of software libraries and toolkits for image processing. - http://www.cs.cmu.edu/~cil/v-source.html