I prefer Common Lisp, but I don't necessarily recommend it for learning functional programming, as imperative and object-oriented programming are just as common in Lisp and functional. Schemers tend to be more functional than Common Lispers, but I still don't think that Scheme forces functional programming on one the way that Haskell or an ML would (in ML's case because it's hard, but not impossible, to do anything else).
If at some point you want to learn (Common) Lisp, I recommend Peter Norvig's Paradigms in Artificial Intelligence Programming. In spite of the title, it's more a study of how to program in Lisp than of AI. And unlike Graham, who has a "funny accent" in his Lisp, Norvig's code is very mainstream.