[SwellJoe]

The book that helped me the most in terms of pragmatic use of functional concepts in real world applications was Higher Order Perl. The examples have been translated into several other languages, if Perl gives you hives (I quite like Perl, but I know it is scary for some folks). It really does a great job of demonstrating from the lowest levels of a functional system (closures, recursion, first class functions, etc.) on up to actually doing things with those basic building blocks.

It is certainly not "pure", but if you're coming from a procedural/OO world mindset, it's a fantastic bridge. That said, it doesn't cover some of the newer features of some modern FP languages, and won't necessarily directly apply to writing in Haskell or ML.