I have just uploaded a new version, 0.13.0.0, of MicroHs to github (MicroHs). The main improvement in this version is that it supports Concurrent Haskell. It has the usual API with, e.g., forkIO to create new threads and MVar to communicate between them. The exception system has also been upgraded to support asynchronous exceptions.
In the future I plan to add more support for using interrupts on microcontrollers running without an OS, to make programming complex interrupt driven tasks easier.