Miller Puckette is the creator of pd as well as a number of other software projects. There is documentation available for pd. He also has a book out called Theory and Techniques of Electronic Music, with online and PDF versions available.
Check out the Pd Repertory Project which aims to provide patches that can run selected pieces of the live electronic music repertory using the Pd program.
Also, a nice interface for an analog synth. I'm doing a lot of thinking about music interfaces lately.
