Functional Programming

All new and at the same time ancient paradigm sent from heavens to save earthlings!
Review: Learn You Some Erlang for Great Good!
This book, although labelled "A Beginner's Guide", belongs on the bookshelf of anybody who is a serious user of Erlang (with the possible exception of those who made the language or who have used it for decades).
Learn You Some Erlang
The best introduction to Erlang you'll get. Written by our very own MononcQc.
Interactive SICP
SICP is a very good book on Lisp and has been around since many years. This website makes it interactive.
High vs. Low Level Languages
There's a lot of mistaken impressions about high level languages, both in terms of their attributes and their benefits. Allow me to elucidate.
Erlang Enhancement Proposals (EEPs)
Erlang docs with search
Search the Erlang documentation
Currying In Different Languages
Snippets of currying mechanisms in different languages which support currying
Curry: a Functional Logic Language
Sure I may be a Mercury fanboi, but there are actually other functional logic languages out there. Curry is one of those. From the blurb: "Curry is a universal programming language aiming to amalgamate the most important declarative programming paradigms, namely functional programming and logic programming. Moreover, it also covers the most important operational principles developed in the area of integrated functional logic languages: 'residuation' and 'narrowing'."
Clojure
A practical derivative of Lisp on top of JVM focusing on concurrency, parallel processing and Java inter-operability.
Adding Textadept Support to Factor
The "Common Learning Initiative" project of #yfl has selected Factor as the language we're going to jointly learn. Factor has some nice tooling for supporting external text editors. Textadept isn't one of these. Until now.