Yudit is a must-have, the best in contemporary Unicode support on Unix and has a lot of features worth imitating. Emacs GNU Emacs 20 includes the MULE multilingual extension which unfortunately avoids Unicode and uses some non-standard internal encoding. Otfried Cheong has already written a unicode.el and utf2mule module to use UTF-8 within GNU Emacs 20.3. There is hope that Emacs 21 will turn to Unicode completely.
Further additions are welcome.