One of my favourite websites currently is Metaculus – it is an opinion/prediction aggregator where players give 1%-99% predictions for the likelihood of various events.
Depending on your prediction and the outcome of the event (as well as the predictions of others) you receive or lose points for being right or wrong.
Increasing your confidence in your prediction increases the amount you can win, but also the amount you can lose – but importantly scores are calculated in such a way that you maximise your expected score by setting the prediction slider to your true belief about the event.
I’ve long been a fan of the idea that prediction markets can provide accurate estimations of the likelihood of events using the wisdom of the crowds, but usually the problem is that people are unwilling to invest money (or be seen to be gambling, especially with serious issues).
Playing for points is low stakes, sure, but lots of people are willing to spend a lot of time and effort to acquire points on the internet elsewhere so I’ve hope that Metaculus grows in popularity.