RHexLib is a general purpose software library for creating real-time control systems. It was originally created to run on the RHex hexapod robot, but evolved to be a more general collection of tools that can be used to build other control systems as well.
For starters, there is a tutorial section for a quick overview of library features as well as a section on Frequently Asked Questions for commonly encountered problems. Below are links to more detailed treatments of features and components provided by RHexLib.