Hoogle is a Haskell API search engine, which allows you to search many standard Haskell libraries by either function name, or by approximate type signature.
Hackage is the Haskell community's central package archive of open source software. Package authors use it to publish their libraries and programs while other Haskell programmers use tools like cabal-install to download and install packages (or people get the packages via their distro).
Learning Haskell is a free Haskell tutorial that integrates text and screencasts to combine in-depth explanations with the hands-on experience of live coding. It is aimed at people who are new to Haskell and functional programming. Learning Haskell does not assume previous programming expertise, but it is structured such that an experienced programmer who is new to functional programming will also find it engaging. Learning Haskell uses graphics programming to create an engaging experience.