In addition to rolling out iOS 6.0.1today, Apple has released a beta build of iOS 6.1 to developers. The update supports legacy devices dating back to the iPhone 3GS and newer products including the iPhone 5 and fourth-generation iPad. A build is not yet available for the iPad mini.
Apple has also introduced a developer preview of Xcode 4.6 to coincide with the iOS 6.1 beta. No major new features have been detailed by Apple in the 6.1 beta changelog, but interested developers can do some digging for themselves by downloading the firmware and Xcode 4.6 from the iOS dev center.