Optar is a software codec that generates 2D bar codes for data storage on paper using a black and white laser printer and scanner. It fits 200kB on an A4 page, uses Golay forward error correction codes to ensure reliability, and can also be used to store data on photographic film.
Mimas Toolkit is a C++ computer vision toolkit. It is easy to use and includes tools for edge detection, corner detection, various filters, optic flow, tracking, blob analysis, Web cam tools for real-time applications, and much more. It also includes many implementations of traditional algorithms such as Canny. It was developed for GNU/Linux but as the GUI is largely separate, porting to other platforms should be straightforward.
Engauge Digitizer is digitizing software that converts an image showing a graph or map into numbers. The image file can come from a scanner, digital camera, or screenshot. The numbers can be read on the screen, and written or copied to a spreadsheet. Highlights for beginners include an intuitive interface and extensive context-sensitive documentation. Highlights for experts include compensation for image distortion, cartesian and polar coordinates, linear and logarithmic coordinates, automatic scanning, graphical previews, and browser help.