I was introduced to SML via Dan Grossman's Programming Languages course [0] and it's quickly become my favorite programming language to work through problems and brain-teasers.
Shame there isn't more non-academic support for it.
That is such a good course. I really enjoyed it and need to go back and finish the third part with Ruby.
If you like SML, check out F#. I did part one of that course in SML, F#, Typed Racket, and Scala. F# was by far the cleanest and most concise for each homework assignment. (Most code was written in SML first and then ported to the other languages.)
Shame there isn't more non-academic support for it.
[0] - https://www.coursera.org/learn/programming-languages