Howdy!
Long time no chat :-)
I will give a talk at the Emacs Conference (emacsconf.org, London March 31) called "How to write an Emacs-based IDE like SLIME".
The idea is to demo SLIME, explain how its development works, and give some encouragement and practical tips to people who might want to build something similar for other languages.
If you have some ideas please fire away :) particularly about things I might easily overlook being as my SLIME know-how is about 10 years old!
Cheers, -Luke