This looks really interesting.
Per the SimpleStateMachine CodePlex site:
"A simple state machine implementation written to replace WF in one of our projects. The interesting aspect of this library is that it comes with a DSL written in boo for quick and easy configuration and management of state machine definitions."
"SimpleStateMachine is a library written in C# that provides an easy to use state machine that can easily be configured via a custom DSL (Domain Specific Language), inspired by an example in a book-in-progess on DSL's by Martin Fowler. SimpleStateMachine's DSL is implemented using Boo and Rhino DSL by Ayende Rahien."
"The motiviation for creating this library was a dissatisfaction with the complexity and weight of Windows Workflow Foundation for creating, maintaining, testing and versioning of what should have been simple state machine workflows in our applications. It is suitable for use both in the user interface and in the middle tier and has optional facilities for directly interacting with your domain model if desired."
Very cool. Download it here.