I'd add that the SML dialect AliceML, influenced by Mozart/Oz, has incredibly nice lazy, concurrent, distributed, logic, etc. extensions. It's really sad it's abandonware:
https://github.com/aliceml/aliceml-alice
and make sure you have all the dependencies installed first, it does build on linux and its fun to play with.
I am currently working on a AliceML derived language and if there is any interest I'll post a note on HN - once its a bit futher down the line.