Two on Kaggle right now:

https://www.kaggle.com/c/data-science-for-good-city-of-los-a...

https://www.kaggle.com/c/jigsaw-unintended-bias-in-toxicity-...

I've also been looking around for something interesting to work on which will actually be helpful to other people. And it doesn't doesn't necessarily need to be ML related.