I've been wondering for a while now, when I finish the game I am working on, if it is possible for it to create a high score list of the people who play it online, and if you can, how would you go about getting it to work?
Your best bet is:
1. Wait for Greenfoot 2.2.0 release
2. Use the new PlayerData class
We're coming along with the release now -- just tinkering with the design of some of the new features, I expect a release early April (realistically).