Forth can be a pretty good way to go about implementing a Lisp, actually. I have a book[1] that uses Forth to build a set of list manipulation facilities inspired by Lisp and then in turn use those to construct a Prolog-like DSL for expressing expert systems. I've actually been tinkering with a pair system in my own Forth dialect that could be interesting if you've ever wondered what recursive list operations would look like in a concatenative language.[2]

[1] http://www.amazon.com/Designing-Programming-Personal-Expert-... [2] http://pastebin.com/q9hMS1rE (warning: WIP)