Game Developers Java Users Group (GameJUG): Mailing lists signup, membership information, resources, and links.
Java Meetup Groups: Find groups in your area. Includes directory, photos, and message board.
Java Robotics Users Group (JRUG): Online group for those interested in the application of the Java programing language for robotics. Includes news, FAQs, and project information.
Java User Groups Worldwide: Sun's JUG page includes index of groups worldwide as well as a finder program.