Like Windows Workflow Foundation?  Scott Woodgate just posted this job advert for a co-worker for me in Product Management forWindows Workflow Foundation.  Follow the link if you are interested.  There are other jobs in workflow going here.  Search for workflow in Redmond, WA at the Microsoft careers site.  Not all of the search results are in the Windows Workflow Foundation team, so you have to sift through the job adverts a bit.