By that I mean languages where they are stable and the standard has stopped being actively worked on, and they offer something interesting by studying them.
I am not looking for normal imperative /procedural languages that have stopped being worked on (i.e. C-like) unless of course it was something that c is based off like ALGOL.
They can be languages that run on any platform (not just unix/osx/win), it can run on a toaster for all I care, I just want it to be something interesting.
I am looking to be amazed :)