Serge Luca wrote following article for MSDN Belux:

Dynamically Start and Kill a Workflow with Windows Workflow Foundation
The Windows Workflow Foundation is a programming model, a run-time engine, and a set of tools for building workflow functionality into .NET applications. Windows Workflow Foundation (WF) is a core component of the .NET Framework 3.0 and can be used on Windows Vista, Windows XP SP2 and Windows Server 2003SP1. In this article, Serge focuses on how to dynamically and asynchrounously start and stop a workflow from within another workflow. He also takes a look at how to pass parameters to a workflow, create custom activities and finally he has a quick look at the WorkflowRuntime Services.

Serge will also host the upcoming MSDN Evening in Luxembourg on March 13 on WF integration with Sharepoint.