The fractal flowers and recursive roots: the most lovely hack I've seen. -- God wrote in Lisp, by Bob Kanefsky and Julia Ecklar
Neomacs is a computing environment based on structural editing. Neomacs aims to become the Emacs of trees. Currently, Neomacs is a usable Lisp IDE and keyboard-driven browser.
To build locally, make sure you have SBCL, quicklisp, and the Ultralisp dist (if you haven't done so, (ql-dist:install-dist "http://dist.ultralisp.org/" :prompt nil)). Clone this repo and https://github.com/ceramic/ceramic under ~/quicklisp/local-projects/. Then (ql:quickload "neomacs") and (neomacs:start).
To build the terminal emulator (currently Linux only), clone https://github.com/neomacs-project/3bst under ~/quicklisp/local-projects/ then (ql:quickload "neomacs/term").
If you are troubleshooting some Neomacs bug, (neomacs:start nil) might be helpful. It turns off built-in debugger and stream redirections and hand it over to external IDE (e.g. SLIME).