Emacs marries Russian

I personally prefer XEmacs (formerely known as LucidEmacs) over GNU Emacs. But the russification of both is actually identical and very easy. However, it depends on what you want to do. My further discussion will be devoted to XEmacs.
If you just want to display and type Russian in XEmacs, you only need to tell it which fonts to use. If you have Cronyx set of fonts installed, you only need to set these X resources (add to your .Xdefaults file):
   Emacs.default.attributeFont: -*-courier-medium-r-*--12-*-*-*-*-*-koi8-r
   Emacs.italic.attributeFont:  -*-courier-medium-i-*--12-*-*-*-*-*-koi8-r
   Emacs*menubar*Font:          -*-helvetica-bold-r-*--14-*-*-*-*-*-koi8-r
Being able to type Cyrillic characters has nothing to do with Emacs itself. You need to do a usual X keyboard layout magic. Consult my X Window notes on that.
Sometimes you might need to use syntax tables in Emacs, for example to change case of sentences, etc. I recommend using a script written by Dmitry Barsky. Address all questions about it to him (D.Barsky@ee.surrey.ac.uk).
There is also a LISP code written for GNU Emacs which you can use. It will display cyrillic letters (if you have an old version of GNU Emacs and make some handy recodings.