The way Facebook's Graph API is structured can be applied to other datasets containing interconnected objects. It's like a REST service serving JSON, with a specific way to construct the URLs. I like it a lot. Here is a blog post explaining the Freebase implementation:

http://blog.freebase.com/2010/04/29/a-freebase-implementatio...

The Facebook docs:

http://developers.facebook.com/docs/api

But even the cleanest API is of no use if the API calls don't actually work...