Pandoc is probably the most well-known Haskell project outside the Haskell community. It's a universal document converter, converting to and from a large number of document formats, including Markdown, RST, Orgmode, HTML, LaTeX, Word and many more. Pandoc is both a Haskell library (useful to create documents) and a command-line program that uses that library.
In this talk, I'm going to give an interactive demo of some of the cooler things you can do with pandoc, as well as talk a bit about its Haskell internals. Its code-base and community are quite beginner-friendly, and contributing to pandoc is a great way to get started with real-world Haskell development.