these guys are crazy; they never sleep :
A workflow engine will be part of the next .Net api (Winfx)
More infos at
now there’s a worflow engine in Biztalk server (they call that "orchestration") and we have the Workflow Foundation.
Choose biztalk for EAI,B2B,scaling environment
Choose WWF for client application,human workflow,state machine (and hey, it’s free !!!!)
What a wonderful world….