Apple has released iOS 9.0.1, a minor maintenance update that fixes issues with the setup assistant, alarms and timers sometimes failing to play, video problems in Safari and Photos, and custom APN setups via external profiles. The iOS 9.0.1 update is available over the air under General, Software Updates in the iOS Settings app.
The second beta of iOS 9.1 has also been released for registered iOS developers, continuing the development of the next iOS update to add developer-level enhancements for the upcoming iPhone 6s and iPhone 6s Plus models. Registered iOS developers can download the iOS 9.1 beta from Apple’s Developer site.
Update (Sept. 24): Apple has now also released the same iOS 9.1 beta 2 as a public beta.