The gitit package
Gitit is a wiki backed by a git, darcs, or mercurial filestore. Pages and uploaded files can be modified either directly via the VCS's command-line tools or through the wiki's web interface. Pandoc is used for markup processing, so pages may be written in (extended) markdown, reStructuredText, LaTeX, HTML, or literate Haskell, and exported in ten different formats, including LaTeX, ConTeXt, DocBook, RTF, OpenOffice ODT, and MediaWiki markup.
Notable features include
plugins: dynamically loaded page transformations written in Haskell (see Network.Gitit.Interface)
conversion of TeX math to MathML for display in web browsers
syntax highlighting of source code files and code snippets
Atom feeds (site-wide and per-page)
a library, Network.Gitit, that makes it simple to include a gitit wiki in any happstack application
You can see a running demo at http://gitit.net.
For usage information: gitit --help