Second, wf.codeplex.com! (This probably classifies as old news, but there is now a general team site on codeplex wf.codeplex.com. Cool!)
So far, it features:
- (new) The WF Security Pack (endpoint blog post) for all your authorization and security credential impersonation needs.
- ADO.Net activities (go with the flow blog post) which I won't pretend to know anything about.
- And the WF state machine (go with the flow blog post) which I wrote about earlier.
Last, on the workflow unit testing front,
Ron Jacob recently posted some WF4 unit testing helpers he created on CodeGallery.
And in case you're not a reader of Kushal's blog, a while ago he had a terse piece about mocking workflows by providing a custom Xaml type resolver which is pretty interesting.