> i'm looking for a minimum list of functions to create a lisp
> interpreter (like picolisp :). which ones to master to grok all of the
> other functions that are built on top of the foundation functions?
I think a lot of the advice, links and references already made in this
thread are very good.
I'd also recommend Peter Norvig's "(How to Write a (Lisp) Interpreter
(in Python))"  and "(An ((Even Better) Lisp) Interpreter (in
Python))" . In the first, he walks the reader through writing a
very small lisp interpreter (90 lines of Python), and in the second he
shows how to make it more robust.