Edwin (the text editor that comes with MIT-Scheme) is not quite emacs, but when I used it for SICP I kind of liked it...once I figured out the debugger. (edit: that sounded sarcastic, I actually liked Edwin)

Apparently there's an important library for the course called scmutils that the Racket people gave up on porting a while back: http://lists.racket-lang.org/users/archive/2005-October/0099...