Clozure CL (formerly OpenMCL)
clozure.com
clozure.com
The only thing that may worry me a little at the improbable case of using it for production code is: strings are encoded in UTF-32!! That's 4 times more memory than necessary for my usual use cases...
Clozure's more or less official announcement was on October 19th, 2007. ( http://article.gmane.org/gmane.lisp.mcl.general/2593 )
Clojure was released on October 17th, 2007. ( http://groups.google.com/group/clojure/msg/16fec21eb1fff8aa )
Of course Clozure is much older if you look at the code and not just the name.