CMUCL is the CMU implementation of Common Lisp.

First-aid documentation is in the manpages lisp(1) and cmucl(1) and
via the normal Common Lisp documentation runtime functions (describe
...)  (documentation ...)  and (apropos ...).  The WWW homepage contains
a pointer to a real user manual.

CMUCL's strength in comparison with other Lisp systems (or most other
dynamic language implementations in general) is its highly optimizing
compiler.  If you know how to write efficient Common Lisp code, you
are free of unwanted memory allocation, type checks, indirections to
objects.  CMUCL helps you to write efficient Common Lisp --- it
generates very informative warning messages about code constructs that
prevent compilation to efficient code.

Optional packages for graphical user interfaces and other Common Lisp
applications and libraries (Eg. the "Hemlock" Editor) are on
ftp://ftp2.cons.org/pub/languages/lisp/cmucl/release/ (FreeBSD-Binaries)
and ftp://ftp2.cons.org/pub/languages/lisp/cmucl/ports/ (source).

WWW: http://www.cons.org/cmucl/