I was able to light up the keyboard using a couple of LED lights actually inserted into and powered by the XO. I just did this and need to find a couple of identical LED lights to use, but it does work and it is very easy to do (for me it was anyway).
I plan on making an "instructable" for this little mod. If I don't get to it I wanted to post how it is done here and let anyone else get after it if they want to. Of course images will be posted if and when I follow through on the instructable.
The quick and easy is this (that is if you know how to take one apart and have done so often).
While the XO is closed there is a piece that comes off when you unscrew it where the battery pack goes.
Well, that is where the LED lights go. There is a gap on both sides of the bracket that holds the screen on. So, if you drill just off to the sides of the bracket with a hole the size of your LEDs then you can remove that piece and take off the top half. Fix your LEDs in place however you want to in the holes of the plastic. Then, run the wires through the bracket with the other wires and connect them to your LEDs. Now run them up to the open 3.3v so called serial developer port. It's open and unused so why not take advantage of it? Just make sure you know which is + or - and then connect it all together. Close it up and poof, your board is lit!
Takes longer to type it all out than this, but that's about it. The instructions will take much longer and the images will take that much more, but I truly hope to do this during the weekend. I have been known to be distracted though. Thus, my typing out the basics of it now.