which language to learn? - The Joel on Software Forum. Of course I had to chime in with my $0.02

If you don't know lisp or scheme I'd recommend one of those (scheme would be my preference) first. Of the three you list I wouldn't pick ADA as it's AFAIK a fairly standard procedural language. Between Haskell and ML I'd probably choose Haskell. It's such a purely functional language you have to start to think functionally, I think ML still let's you code imperative code if you want to. On the other hand, Haskell is, IMHO, difficult to find practical applications for, that is it is difficult to interface with the outside, generally imperative, world. If you go with ML you can use OCaml, which offers all sort of programming paradigms in one box. Personally I wouldn't bother with perl, python, or ruby if you want to learn anything beyond a new syntax. Sure they're all slightly different from each other but no where near as different as scheme or haskell.