StandardML is a great language to teach (functional) programming. It has a robust type system with great inference capabilities as well as a small language definition well suited to learning main FP concepts.
Python GUI Support
GUI support for python, stuff like: Kivy, PyGoObject, GTK3, ect. We already have TKinter, maybe implement the same for other frameworks.
How about adding Arc language?
Hi repl.it guys, It would be very nice if you could add Paul Graham's Arc language (see http://arclanguage.com/ ) into your language palette. Arc is beautiful and lisp-like language, it has a repl, so I think is suitable for inclusion on your site.