[1]: http://www.newlisp.org/
Runners up are Racket and Guile.
The "Lisps in Python" (like Hy and Hissp) are nice, but they're not very Lispy. More like Python with sexpr syntax. For Lisp on a Python runtime, I recommend Calysto Scheme for messing around: https://github.com/Calysto/calysto_scheme
It's slow, but it's full Scheme.