Maybe the following paper is of some interest to Poly/ML users:
Makarius Wenzel. Parallel Proof Checking in Isabelle/Isar. In G. Dos Reis and L. Th?ry, editors. The ACM SIGSAM 2009 International Workshop on Programming Languages for Mechanized Mathematics Systems. Munich, August 2009. To appear in ACM Digital library. http://www4.in.tum.de/~wenzelm/papers/parallel-isabelle.pdf
The full system sources are available here (large): http://isabelle.in.tum.de/repos/isabelle/rev/Isabelle2009
The actual parallel programming library is here: http://isabelle.in.tum.de/repos/isabelle/file/Isabelle2009/src/Pure/Concurre...
Makarius