One of the best, for sure. There are Racket and Clojure in the Lisp family, both comparable to Common Lisp in terms of features. Outside of that, there is Elixir, which in my mind gave Erlang enough additional features to also finally be at that level. Pharo is another language - a modern Smalltalk-inspired, image based GUI environment - which comes close in terms of expressivity, but is nowhere near CL implementations in terms of stability. There's also REBOL and recently also Red. They all differ, of course, but what they have in common is the amount of features such languages offer and the unique kind of synergy you get from each of them. It is still unmatched by currently mainstream dynamically typed languages.

> you might appreciate my functional collections library for CL

Thanks, looks interesting. I'll take a look later. I think one of the most irritating things when I started learning Common Lisp was weird naming of common functions. In Emacs Lisp-land we got dash.el and s.el which made the situation (mostly) better; similar thing was done by Underscore.js. I think something like this could be helpful in CL - maybe your library could fill that role for me.