How do I set up a Haskell programming environment?

Hackage is a community-run package repository for Haskell packages to which anyone can upload their work. Cabal is a ubiquitous build system for Haskell programs (like Make, only specialised for Haskell) and Cabal-Install is a program built on top of Cabal that provides a command line utility (the cabal program itself), which notably has the ability to automatically download required package dependencies from the Hackage repository.

The Haskell Platform is a bundle of GHC, the most popular Haskell compiler, and some of the most widely used Haskell libraries and tools, and the recommended way to bootstrap a Haskell environment. After the Haskell Platform has been installed, further packages from Hackage can be installed via Cabal, for example by running cabal install sindre at the command line. These will be installed in the .cabal directory (most likely in your home directory) and installation does not require root permissions.