I wrote a simple and easy to use local high score system for some of my games and I thought I'd share. I also have support for global high scores in the works using google app engine. When I ever get some time to finish the global stuff it'll be very similar to cocoslive.net.

Scores are timestamped, sorted by score and stored as json. There is a dynamic grouping system to allow for on the fly generation of scoreboards.

The end goal will be to make local and global high scores completely transparent and to make them as easy to work with as possible.

Check the readme for some code examples:
http://github.com/Abica/lime

Let me know what you guys think.