CEJavaComm A driver implementation for the Java Communications API for the WindowsCE/Pocket PC architecture. This driver supports RS232 (serial) ports (and possibly IRCOM but untested).
Java API for FireWire A Java API for controling 1394 Digital Cameras (based on libdc1394 library). [Open source, LGPL]
JButtons Java framework for controlling iButton and MicroLAN 1-wire devices. [Open Source, BSD-like]
RCXComm Java package for communicating with the Lego Mindstorms RCX Brick. The core of the RCX Brick is a Hitachi H8 processor that can be controlled in a variety of ways to read sensors, activate motors and do general processing. [Open Source, GPL]