GCL
GNU Common Lisp is a Common Lisp implementation of the KCL Family that uses gcc to compile Lisp into native binaries. GCL started out as a CLtL1-level CL; steady progress is being made towards bringing it to ANSI CL compliance: It is almost there now. CVS head is rather close to compliance.

GCL is released under the terms of the LGPL and is the official common lisp of the GNU System. It runs on twelve GNU/Linux architectures (x86 amd64 powerpc s390 sparc arm alpha ia64 hppa m68k mips mipsel), Windows, Sparc Solaris, FreeBSD, and Mac OS X. GCL has support for cross-platform graphical user interfaces using the Tk widget set.

GCL is closely associated with the Maxima, ACL, ACL2, and Axiom projects.

GCL is under active development: the last version was released in September 6, 2014. The project is a GNU Savannah project and uses the GIT version control system.

The current stable release of GCL (gcl-2.6.12.tar.gz) is 2.6.12, and can be downloaded from GNU's FTP site. You can check out the GIT development source tree using the following commands:

git clone git://git.sv.gnu.org/gcl.git
cd gcl
git checkout master
cd gcl

You can download a MS Windows executable (".exe") and get other information for using GCL with Windows here.

The official home page has release notes and describes more of GCL's features (X, MPI, flexible C FFI).