Microsoft released the Training Kit for developer yesterday. It contains presentations, Hands on Labs and democode for the new Windows 7 APIs.     
The Traing Kit is directed towards to C++ developers, but Microsoft offers Wrapper classen for .NET.
Topics:
- Taskbar
 - Libraries
 - Multi Touch
 - Sensors and Location
 - Ribbon
 - Trigger Start Services,
 - Instrumentation and ETW
 - Application Compatability
 
.NET Devs:
Some API will be integrated into the .NET 4.0 Framwork, e.g. Multitouch input, the taskbar & jumplists in WPF. With the Wrapper from Microsoft you gain access to the other APIs. The wrapper classes are open source (and are not supported by Microsoft!).