Great (and free) Lisp programming environment

It is good to know more than one programming language: Common Lisp is one of my favorite languages and I often encourage other programmers to learn it. Peter Seibel (author of " Practical Common Lisp" and well known in the Lisp community) has put together a complete programming environment LispBox that integrates a free Lisp development system (CLisp, OpenMcl, or AllegroLisp) for Windows, OS X, and Linux. He included Emacs, Slime, and ASDF (a package system for automatically loading systems from the web).

Neat stuff and a huge time saver if you want to set up your own Lisp development system.