Nice list! I remember HN talking about https://students.brown.edu/seeing-theory/ when it came out but sadly it seems like this website was discomissioned.
Added an entry for my data visualisation tool here: https://github.com/stared/interactive-machine-learning-list/....
Edit: found an updated link for seeing theory so I fixed it in the PR above. Feel free to cherry-pick if #24 is not relevant.