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 Note that many of the navigation pages are missing or out of date.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