Books
Haskell: The Craft of Functional Programming, Simon Thompson - This is a typical text book about learning Haskell. It is aimed at the new comer and does a very good job of teaching the practice and principles of programming in functional languages, with Haskell in mind.
This is the book I read when I first learned Haskell.

Papers
Why Functional Programming Matters, John Hughes - A very popular paper that examines why we should bother with functional programming at all. It examines some techniques at a rather more advanced level (and it's not even using Haskell) than the Why Does Haskell Matter paper presented at this site.
Side note: The author of this paper was my professor in the introductory Haskell course at the school I'm attending.

A gentle Introduction to Haskell, Paul Hudak, John Peterson, Joseph H. Fasel - An excellent paper on many aspects about Haskell. Probably not as "gentle" as the newcomer would like. It is intended as a light-weight version of the Haskell 98 report, so some knowledge of functional programming is recommended.
A good read once you've learned the basics of functional programming!

Tackling the Ackward Squad: Monadic Input/Output, Concurrency, Exceptions, and Foreign Language Calls in Haskell, Simon Peyton Jones - This paper examines some of the stickier issues of functional programming - dealing with the outside world, for instance. It dissects a case study of programming a web-server in Haskell, an application that does almost nothing but IO, and does so concurrently. Along the way they go through IO, Concurrency, Exceptins and Foreign Language calls in reasonable depth.