Apple has released iOS 8.1 beta 2 to developers. The update is available through the Apple Developer Center, as well as over the air on devices running the first beta of iOS 8.1. The first beta of iOS 8.1 was seeded just over a week ago.
To update over the air, go to Settings > General > Software Update and selecte Download and Install. The only notes for the beta is that it contains bug fixes and improvements.