I'm not sure about aiming for "pure" languages. Lisp is functional enough that one can learn pure functional programming using it, if he tries. And Ruby is OO enough that one isn't missing much, isn't it?
Nothing wrong with the pure languages as options, just I think impure languages can fit the categories too.
I would recommend Ruby, too. Even though I don't write large programs or webapps in Ruby, I use it to write the occasional script to glue different things together.
I think that there's probably more (practical) benefit to be had with Ruby than Smalltalk or Self.
Nothing wrong with the pure languages as options, just I think impure languages can fit the categories too.