Here are a few resources that can help you learn more about Mind Mapping and GTD...
David Allen Webinar
GTD & MindManager My own use and some map examples
Some useful GTD add-ins to consider:
Gyronix (GyroQ, Results Manager)
TPAssist (TPAssist & TPAssist Capture)
Also, the brain uploads MindManager maps so it could be possible to leverage both as well!
Good luck and I'm happy to answer any mapping questions you may have.