Wikipedia
VXL
VXL, the Vision-something-Library, is a collection of open source C++ libraries for computer vision. The idea is to replace X with one of many letters, i.e. G (VGL) is a geometry library, N (VNL) is a numerics library, I (VIL) is an image processing library, etc. These libraries can be used for general scientific computing as well as computer vision. Some examples of usage can be seen online.