Here they are: https://channel9.msdn.com/Events/Build/2012

Well, these are mostly about Windows 8, and some about dev tools, Windows Azure.

No Windows Phone 8 sessions yet, except this super interesting one:

Deep Dive into the Kernel of .NET on Windows Phone 8

https://channel9.msdn.com/Events/Build/2012/3-005

The CoreCLR is the cutting-edge virtual machine at the heart of the .NET in Windows Phone 8. In this session, we'll dive deep under the covers of the .NET runtime engine and discuss some of our key innovations for .NET on Windows Phone 8. Topics will include our compiler in the cloud, WinPRT via .NET, Async and performance improvements.