Jabberwocky is a development environment for Lisp programs. It includes a Lisp aware editor, a source level debugger and a way to interact with Lisp processes.
CSharp (C#) Development Environment for XEmacs / GNU Emacs
A bundle of lisp extensions, largely original, for GNU Emacs with the goal to obtain a more user friendly and powerful interface. The new features include contextual tool bars, new TeX interface, very complete menus, and a well structured IDE.
XEmacs is a highly customizable text editor and application development system. Its emphasis is on modern graphical user interface support and an open software development model.