http://developer.apple.com/iphone

Updates to the Push API that is coming later this year, GPS updates rumored to be getting prepped for turn-by-turn:

A few new things we are seeing in this version of the software is the addition of a bunch of Core Location features that track the direction you are heading, and the speed you are traveling.

The notes state you cannot use this toolchain to build apps for the App Store, and apparently the link to the NDA is gone. (Via GearLive)