The new beta, build 14C106a, is available through the Software Update mechanism in the Mac App Store and through the Mac Dev Center.
As with previous betas, Apple asks developers to focus testing on Wi-Fi, Mail, Bluetooth, and VoiceOver. Many Yosemite users have had some ongoing problems with Wi-Fi since the new OS was first launched in October, and a November 10.10.1 update did not resolve all of the lingering issues.
