Tonight i spent some time at Hackspace Manchester reverse engineering the keyboard matrix on our speak and spell, in preparation for hooking it up to an MBED. Since nobody else has released this information (as far as i can tell), here is the pinout:
This means that when the 'off' button is pressed, for example, pin 1 and pin 5 will be connected together.
To read a matrix keyboard like this, we write some code that steps through the 'down' set of pins (1, 2, 11, 12, 13), holding them low one at a time, then checks each of the other pins (3-10) to see if anything is being held low. If so, we perform a lookup on the table above.