Hi, I just wanted to let you know that I made a small Java wrapper around the wiringPi library for accessing the GPIO ports. You can download the project from here: https://github.com/jkransen/framboos
It's a day of work, so there are plenty of sharp edges, but I was able to light up LEDs and respond to button clicks from the code. I'm using the SK Pang starter kit, because it includes a tailored housing and a breadboard, but you can get the basic components from anywhere.
I'm hoping to get it to a state where beginners can easily add new classes with their own algorithms to make the lights go on and off in a specific pattern. That would be a fun way for kids to learn programming.
For more info, see my blog post about this: http://jkransen.wordpress.com/2012/07/16/raspberry-pi/