If you are looking for some introduction material to Microsoft Workflow Foundation 4.0 then here are a couple of links and tips.
Windows Workflow Foundation (WF) Overview Wiki
Windows Workflow Foundation (WF) Screencasts:
Endpoint TV screen cast:
Blogs that I follow for updates and development tips on WF 4.0
Andrew Zhu Blog - http://xhinker.com/
Ron Jacobs - http://blogs.msdn.com/b/rjacobs/
WF 4.0 is much more Unit Testing friendly. Ron Jacobs created WF 4.0 Unit Testing Helper library that is available at http://code.msdn.microsoft.com/wfth/
Microsoft WF 4.0 Forum - http://social.msdn.microsoft.com/Forums/en/wfprerelease/threads
Using WF 4.0 with WCF 4.0 is one of the greatest experiences I have so far and one powerful toolset to know. These details should get you started with WF 4.0.
After you understand WF 4.0, I suggest you start looking at Microsoft AppFabric technology stack.