New guidelines outline what iPhone data Apple can give to police

The guidelines themselves are readable, interesting, and in HTML, so perhaps the primary source is better than the secondary in this case:

http://www.apple.com/legal/more-resources/law-enforcement/

The context behind these guidelines: if Apple has some piece of information, they can't (really) decide whether to yield them in response to a search warrant. These aren't the things Apple feels comfortable providing; they're the things it's capable of providing.