The Bridge Board v2 is an add-on which makes it very convenient to use a JeeNode (or a JeeNode USB, or a SMD Kit) alongside a solder-less breadboard, by bringing all pins out to the side - clearly labeled for easy access.
This board contains 2 LEDs with current-limiting resistors, as well as a push-button. These too are brought out to the side, and can be used for any purpose (the push-button makes a nice reset button if you have the PSIX or SPI/ISP connectors hooked up).
Depending on how many headers are connected, you get access to up to 18 I/O pins on the ATmega. All pins are labeled, with extra labels using the Arduino pin numbers for easy reference. There is room for optional FTDI (+ cap) and SPI/ISP headers on the board.
The Kit version includes the PCB, low-current LEDs + resistors, a push-button, and enough headers to connect all the 4 JeeNode ports and all the pins on the breadboard side, including the top power rails.
The PCB only version contains just the board for the Bridge Board. No parts, no headers.
The documentation and full design details are freely available.