Wow, CTP1 of WF Security Pack is gone live now. Go get it from:

 http://wf.codeplex.com/releases/view/48114

Check out following post for an introduction. 

http://blogs.msdn.com/b/endpoint/archive/2010/06/30/introducing-the-wf-security-pack-ctp-1-on-wf-codeplex-com.aspx

My blog also has a slightly old intro post.

http://zamd.net/2010/02/23/introducing-workflow-security-pack/

Over the next few days, we will cover all the interesting scenarios enabled by WF Security Pack. Stay tuned...  Please let us know what do you think about this pack. This would help us bring this functionality in next version of .Net Framework.