HasClunk is a very lightweight blog generator made in Haskell. It supports posts, pages, categories and RSS. You can write your posts in whatever format you like and setup your conversion shell command in the config. Templating is simple, just a header.html and a footer.html that will sandwich your posts and pages. You can use special tags like {base_url} to refer to the blog's url that is setup in your config file.

The Haskell code is clean, well-documented and uses very little dependencies (to avoid Cabal Hell). All the internally generated HTML5 is put in one Haskell file (Html.hs), which you can edit, but you'll probably find that editing the default css and template will fit your needs.