Thanks to Pastor Erick at Joyous Exchange for alerting me to this surprisingly comprehensive collection of resources on vocation: Monergism :: Vocation & Work.
It includes hard to find but exceptional material from Steve Hein and John Pless, as well as a series of brief articles that I have written on the subject.
The links includes treatments and applications of the doctrine of vocation from both Lutheran and Reformed perspectives. Sample some of both. What are the differences?