A textbook that I (JM) recommend warmly, is Graham Hutton's
Programming in Haskell, 2nd ed., Cambridge University Press,
2016, ISBN 978-131662622. Recommended. Comes with pre-recorded lectures by the author (link on the textbook page).
Another, slightly more advanced textbook is Richard Byrd's Thinking Functionally with
Haskell, Cambridge University Press 2015, ISBN 978-1-107-45264-0. Auxiliary reading.
Yet another one-hour lecture, given
in FOO Café in Malmö, this time by Erik Meijer. The title was: "Category Theory, The essence
of interface-based design". Fun.
The Haskell web site is the general
starting point for finding Haskell related information on the web.
However, there is also an alternative Haskell web site,
with resources related to Haskell.
The official definition of the language and its standard libraries is the
Haskell report.
The pointer to documentation of lots of Haskell library modules
is here.
A summary of "what is a monad", with a couple of interesting links:
Ask HN.
