Written by three of the most prolific and capable Haskell library developers. It covers everything from introductory functional concepts to high-performance C-style stateful programming.
You can buy a dead tree, or read it online for free.
the pros of the book is that it offers a good introduction to the language and a reasonably good survey of some of the more advanced language features and tools such as QuickCheck, STM, concurrency/parallelism, etc.
the cons are that it leaves out one very new interesting direction called functional reactive programming, FRP, and i also thought its treatment of monads (esp. monad transformers) to be a bit thin. most of the time i just found myself going to publications on the more advanced topics than using a book such as RWH (or learnyouahaskell, which i actually quite like).
here are a few links i came across in the course that i think are worth sharing (in no particular order):
(1) http://www.cs.nott.ac.uk/~gmh/monads
(2) http://www.cs.nott.ac.uk/~gmh/monparsing.pdf
(3) http://www.grabmueller.de/martin/www/pub/Transformers.pdf
(4) http://pubs.doc.ic.ac.uk/error-handling-for-Haskell/error-ha...
(5) http://horna.org.ua/books/All_About_Monads.pdf
(6) http://web.cecs.pdx.edu/~mpj/pubs/springschool95.pdf
(7) http://www.cse.chalmers.se/~rjmh/QuickCheck/manual.html
some papers on FRP: http://conal.net/papers/icfp97/icfp97.pdf
this below is a link to a postscript version of "functional reactive programming from first principles", by hudak. http://j.mp/hkk6VC
and, finally, yet another haskell tutorial: https://secure.wikimedia.org/wikibooks/en/wiki/Haskell/YAHT
*EDIT: attempted to purtify multi-link mayhem.
I am hopeful that Learn You a Haskell will serve as a good introduction to Haskell, and will recommend it to anyone interested.
RWH is still a fine book; once you understand Haskell, it's still great to go through the examples and exercises. But it is not a good starting point.
For someone who's done some functional programming before, Real World Haskell is probably a good starting point; otherwise something like YAHT would probably be better.
A very enjoyable tutorial. Supposedly, this site was going to come out in book form. If/when it does, it should become the de-facto "Camel book" for Haskell.
My vote would be for Richard Bird and Phil Wadler's Intro to functional programming using Haskell.
You should definitely check it out. If you already know Haskell and you love algorithms, that book will probably be more interesting than the Intro to Haskell book.
Also check out Okasaki's book of functional data structures: http://www.amazon.com/Purely-Functional-Structures-Chris-Oka...
However, I prefer Bird/Wadler better because there's a pervasive "let's derive this"/"let's prove this" approach to the topics. By which I mean, given a spec, let's derive a program that does the task (and later, let's optimize this function using laws we know such as relations between map and filter, the laws of fold). Hutton takes this type of approach only in his final chapter.
Hutton is definitely easier, and does a better job of teaching you the core of Haskell, however Bird/Wadler teaches you how to derive programs from spec (further covered in Bird's Pearls of Functional Programming book).
I think the difference is like the one between How to Design Programs and Structure and Interpretation of Computer Programs.