Gimp Mode is an Emacs mode for developing scheme scripts for the GIMP Image Manipulation Program (script-fu). It is very much aimed at discoverability, aided by a help system inside Emacs and fuzzy completion.
You can get Gimp Mode at github:
git clone git://github.com/pft/gimpmode.git
http://eric.lamarque.free.fr/?linux/gimp-shell.el is an older emacs shell for GIMP.