GeoKalk (was GeoCalc) is a calculator for vectors (lines, planes, and oriented drillcore data), and tensors (strain and stress). Vectors operations can be visualised in a Stereonet, and tensor operations in a Mohr Circle. Besides being a great tool to learn vectors and tensors operations, GeoKalk is a powerful tool to perform batch operations on thousands of vectors or tensors stored in text files.
GeoKalk was made for geologists, but it can be used by anyone interested in vectors and tensors (engineers, physicists, mathematicians, etc.).