The download links are still propagating but they are live on the dev site now.
- WWDC 2011: Hurah, Apple re-imagines iPhone notifications in iOS 5! (9to5mac.com)
- Real or fake, cool photo depicts new iOS 5 notification system and Twitter integration (9to5mac.com)
- Apple has begun widespread testing of iOS 5 (9to5mac.com)
- WWDC 2011: Apple shows off Twitter integration in iOS 5 (9to5mac.com)