According to Freshmeat.net announcement, version 0.20.0 of the Open RObot COntrol System (OROCOS) has been released. This is a major update that includes "refactoring of the API, validation and improvement of the realtime scripting language, and improvement of the overall realtime performance." The documentation also include major updates. The OROCOS project provides two tightly integrated pieces of software. The first is a realtime control framework and the second is a robot control package consisting of class libraries for control, motion generation, kinematics, dynamics, and other robot-specific algorithms. OROCOS is Free Software licensed under the GNU GPL. If you've been thinking about building a PC-based robot, this would provide a great software base to start from.