The WCF/WF 4 training kit contains a set 6 hands on labs that will help you quickly get up to speed with Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) in .NET 4. The labs include Introduction to Workflow, Workflow Services, Flowchart, Workflow Designer, Service Discovery and Monitoring.
http://code.msdn.microsoft.com/wcfwf4/Release/ProjectReleases.aspx?ReleaseId=2698
Get the VS2010 Samples here http://msdn.microsoft.com/en-us/vstudio/dd238515.aspx
Updated 22-05-09:-
Parallel Extension Samples http://code.msdn.microsoft.com/ParExtSamples
Visual Studio 2010 and .NET Framework 4 Training Kit http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=752cb725-969b-4732-a383-ed5740f02e93
IronPython 2.6 CTP for .NET 4.0 Beta1
DSL tools http://code.msdn.microsoft.com/DslTools