Windows SDK samples for WCF and WF are updated for .Net 4 Beta 2. These’re only samples that’re new or changed in .Net 4. If you want complete set of existing samples as well you'll need to pick those up from platform SDK. You can also get online documentation for new .Net 4 samples from MSDN. Note that many of navigation pages’re missing or out of date. If documentation for a sample doesn't appear to be included in a section, look at navigation menu on left hand side to see if more topics’re listed for section there. The individual sample documentation’s available even though section summaries haven't been updated yet.

Download: Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4.0 Beta 2
Download: Windows Communication Foundation (WCF) Samples 4.0 Documentation