IDE for Interlisp and Common Lisp
Online IDE for Interlisp (and Common Lisp).
A programmer's editor written in Common Lisp, written for Common Lisp, which aims to be a good Common Lisp IDE; but which also works as an IDE for other languages too.
Think Emacs in Common Lisp.
It's a Forth. It's a Lisp. It's lambda calculus. It looks like fun and also something I'd never actually really use.