ILISP is ``a comprehensive (X)Emacs interface for an inferior Common Lisp, or other Lisp based languages.
``Currently ILISP can handle the connection with the following Common Lisp and Scheme implementations: CMUCL, CLisp by B. Haible and M. Stoll, Harlequin LispWorks, Franz Allegro CL, many KCL derivatives (including GCL), and various Scheme implementations. ''
You can find out more at http://ilisp.cons.org/ or download it from http://sourceforge.net/project/?group_id=3957
For a long time IlispMode had the dubious honour of being "just good enough"; although very easily confused and with viciously opaque failure modes, it was sufficiently good that nobody was motivated to write anything better. Happily in late 2003 a new project - the Superior Lisp Interaction Mode for Emacs, or SLIME (SlimeMode) was created, which as of May 2004 though still pre-1.0 is about ready for real work and already more useful for many people than ILISP.