Apple has just released iPhone OS 4 SDK beta 2 on developer.apple.com for developers. Update: Here's the official word:
iPhone SDK 4 beta 2 and iPhone OS 4 beta 2 are now available from the iPhone Dev Center. The new iPhone SDK introduces an auto-provisioning feature that allows you to add a new device in a single step from within the Xcode Organizer, making it even easier to enable a device for testing your applications. View the Xcode 3.2.3 Read Me for more details on this feature.
It's great to see the 2 week schedule is being kept up, which means there should be several more leading up to a final, gold master seed at WWDC in 2010 and public release sometime to follow -- probably alongside the 4th generation iPhone.
For more on iPhone OS 4, see TiPb's complete iPhone OS 4 preview and feature walkthrough. No doubt code-diggers are already at work looking for even more in the newest release, so we'll update when the finds come in.
If you notice anything, let us know in the comments!