Armed Bear Common Lisp
Armed Bear Common Lisp (ABCL) is an implementation of ANSI Common Lisp that runs in a Java virtual machine.
GNU CLISP is a Common Lisp implementation available on a wide range of architectures and operating systems, including Unix/Linux and Windows. It is distributed under the GNU GPL license.
Emacs Common Lisp (NaCL)
Emacs Common Lisp is an implementation of Common Lisp written in Emacs Lisp.