Franz Allegro is a CL compiler available for Linux, Unix, and Windows. Free versions are available.

Interpreter and FASL compiler, portable ANSI Common Lisp implementation, CLtL2 conformant, available for many platforms; multilingual user interface. [Open Source, GPL]

Implementation of Common Lisp programming language, runs on most major Unix platforms, mainly conforms to ANSI CL standard; fast compiler outputs native code code of near C speed; powerful module system, data structures. [Freeware]

World Wide Web server implemented in CL; goal: to rapidly prototype, smoothly evolve experimental, novel, or complex applications for the WWW. [Open Source]

Not a Common Lisp system, compiles Lisp programs into working C programs; coded in Lisp; supports strict, very large subset of Common Lisp + CLOS. Descriptions, documents, downloads. [Open Source, GPL]

Corman Lisp and PowerLisp compilers with support for 68k and PPC Macs. [Shareware/Freeware for personal use]

Makes Macintosh Common Lisp, MCL: for 68k, PowerPC; compiles to native code, supports threads, integrates well into Mac OS, fun; Common Lisp Interface Manager, CLIM: platform independent user interface system, to target other Lisp platforms.

(FTP) An implementation of Common Lisp designed for being embeddable into C based applications.

(FTP) A GPLed Common Lisp interpreter.

A shared library implementing a Lisp dialect that is lightweight, reasonably fast, and highly extensible. It contains an interpreter, byte-code compiler and virtual machine. Applications may use the interpreter as an extension language, or it may be used for standalone scripts. [Open source, GPL]

Provides a full native implementation of Common Lisp Windows, Linux, Unix.

An interpreter for the IsLisp language. Free for non-commercial use.

An open-sourced Common Lisp implementation for LinuxPPC.

A version of Berkeley Franz Lisp for 386-based NetBSD systems.

Minimilist Lisp dialect and virtual machine. Reference, tutorial, FAQ. Downloads. [Open source, GPL]

An interpreter for a lexically scoped minimalistic Lisp of Lisp 1.5 type. It written in C++ and currently runs under Linux. [Open source]

A free DOS-based Common LISP implementation with CLOS from Sapiens Software. Site includes a comprehensive reference manual for Common LISP.

A multi-threaded CL supporting SMP Unix systems.

Common Lisp development system. Includes command-line and IDE Lisp interpreters. Possibility of creating EXE-files. [Free for non-commercial and education use]

Implements Common Lisp for Linux on x86 hardware, has large subset of Common Lisp as a shared library that can be linked with Lisp and C code to make efficient, small programs; suitable for embedding in other programs.

An integrated cross-platform development tool for ANSI Common Lisp. [Free and commercial versions]

A version of Lisp based on the experimental XLisp.

Based on XLisp, but with built-in statistics support.