In a comp.lang.lisp thread about “the best product (or freeware) for developing Lisp applications”, Marco Baringer gave a pretty concise reply [seen at Bill Clementson's weblog], one that put a bit more of a stake in the ground and is therefore somewhat more useful than the true, but unwelcome “it depends”.
I took Marco's answer and shortened it even further, extracting what I felt was the most important advice, and then adding a little bit of my own. This, then, is my advice, based on Marco's but changed enough that he should not be blamed, to people interested in trying Lisp for the first time:
Posted by jjwiseman at October 29, 2004 01:11 AM
As far as the commercial implementations go, I've never heard anyone complain about Allegro, LispWorks, or MCL. As far as the open source stuff goes, if you're on x86 *nix, pick one of CLISP, CMUCL or SBCL. If you're on PPC, try OpenMCL.
If you're just starting out, I'd suggest grabbing one of the free commercial trial versions as they tend to Just Work.
The commercial Lisp products tend to have either pretty good IDEs or good emacs interfaces. If you're using an open source Lisp, you can pick between Emacs+SLIME, Emacs+SLIME and, should you feel daring, Emacs+SLIME. Seriously, there's really no other option when it comes to open source Lisp development.