I've been working with James Newton, of Linnistepper fame, on an open source commercial low cost closed loop motor conversion system. An encoder board is available for sale, along with a PIC based PID controller.
The relevant links are here:
This project may also be of interest to some of you. It is a low cost 40V 18A H bridge based on the same FET driver as my smaller servo drive project, with some easier to cool transistors.