I would guess the 14 pin header near the top is JTAG and the 6 pin header in the middle of the board is serial.
Use a multimeter on the serial to find GND and VDD, then look for two other pins, one of which will be an input (so will show a much lower voltage than VDD, unless it has a pull-up resistor), and the other one will be an output, which will probably be VDD when idle. Look for activity on the output when booting - if you get some, then hook up a serial adapter (make sure you have the correct VDD - it's usually *NOT* a +/- 12V RS232 port but more likely a 3.3V logic level port) and check various baud rates on boot to see if you can see the bootloader and kernel messages.
-- Rod
(Last edited by rwhitby on 11 Jul 2008, 03:22)