I'm in a BizTalk 2006 class this week, and the instructor is Jon Flanders, who is quite well-versed in all things BizTalk (probably an understatement). Jon has a blog at http://www.masteringbiztalk.com/blogs/jon/default.aspx, so if you're interested in learning more about either BizTalk or Windows Workflow Foundation, you might just want to subscribe.

Jon also offers some nice tools and samples on the site.