Apple has had a number of updates pushed through the pipeline today, and the latest comes in the form of their iOS 5 SDK beta. The updated SDK (software development kit) allows developers to tap into features included in iOS 5 and future beta releases.
Developers working with the iOS 5 SDK beta have access to app integration with iCloud Storage, Newsstand Kit, Core Image, GLKit, Twitter, and new Game Center APIs. iOS Developer Program members can log in to download iOS 5 beta files and the new iOS 5 SDK beta from Apple's iOS Dev Center.
If you notice anything specific just drop into our iOS Developer Forums and let us know!