Several documentation systems provided the inspiration for Haddock, most notably:

and probably several others I've forgotten.

Thanks to the following people for useful feedback, discussion, patches, packaging, and moral support: Simon Peyton Jones, Mark Shields, Manuel Chakravarty, Ross Patterson, Brett Letner, Sven Panne, Hal Daume, George Russell, Oliver Braun, Ashley Yakeley, Malcolm Wallace, Krasimir Angelov, the members of <haskelldoc@haskell.org>, and everyone who contributed to the many libraries that Haddock makes use of.