Apple has just released iOS 4.3 Beta 2 and the Apple TV Software Beta 2 alongside. The beta versions are only available to those who pay for a developer license ($99 a year) and feature pre-release software designed for developers to test out their applications on iDevices. The Apple TV Beta is so that they can test AirPlay streaming between Apps and Apple TV.
You can check out Apple's developer page, here. We will be keeping an eye out for anything new to this build.