I downloaded this a long time ago. I lost interest in lisp, but I keep it around at work and home because it makes a damn fine calculator, especially when you have a multi-step problem. You can just type it in in the order that you would say it out loud, whereas on a normal calculator (like calc.exe) you have to rearrange it to suit standard order of operations.
http://www.macupdate.com/info.php/id/26203/ready-lisp
SBCL bundled with Aquamacs, a version of Emacs designed to integrate with the Mac interface (including Mac keyboard shortcuts).