Apple today released the third beta of iOS 6.1 to developers. The release has a build number of 10B5117b, versus 10B5105c for the second beta of iOS 6.1 that was released on November 12.
Apple also released a beta of the Apple TV software, as well as Xcode 4.6 Developer Preview 3. Registered developers can download the betas via Apple's Developer page or via Software Update on iOS devices with a previous iOS 6.1 Beta already installed.
Article Link: Apple Seeds Third iOS 6.1 Beta to Developers