I haven't ever done anything too significant in Haskell, but the Jekor Redo [1] videos are fantastic, and demonstrate the slow building up of more complicated things than "reverse this string." I haven't watched his xmonad [2] or pandoc [3] videos yet, but I would bet that they are highly worthwhile as well.
- 1: https://www.youtube.com/watch?v=zZ_nI9E9g0I
- 2: https://www.youtube.com/watch?v=63MpfyZUcrU
- 3: https://www.youtube.com/watch?v=nCwG9ijQMuQ