IDoc extracts interface documentation and declarations from Haskell modules
based on standard Haskell layout rules and a small number of clues that the
programmer embeds in interface comments. These clues have been designed to be
visually non-imposing when displaying the source in a text editor. Interface
documentation is rendered in standard markup languages (currently, only HTML is
supported). IDoc has been designed to be simple to use and install.

WWW: http://www.cse.unsw.edu.au/~chak/haskell/idoc/