Steel Bank Common Lisp - Steel Bank Common Lisp (SBCL) is a high performance Common Lisp compiler.

CLISP - CLISP is a portable ANSI Common Lisp implementation and development environment by Bruno Haible.

Allegro CL - Leading commercial Enterprise Development Tools and dynamic object-oriented Common Lisp development tools including Allegro CL with AllegroCache, an Object Database that provides Object Persistence in Lisp, native to the Lisp langauge.

CMU Common Lisp - CMUCL is a high-performance, free Common Lisp implementation.

Racket Lang - Racket (formerly PLT Scheme) is a modern programming language in the Lisp/Scheme family, suitable...

Clozure Common Lisp - Clozure CL (often called CCL for short) is a free Common Lisp implementation with a long history.