Metaculus, founded in 2015 by cosmologist Anthony Aguirre with Greg Laughlin and Max Wainwright, is a reputation-based forecasting engine rather than a money market. Forecasters submit probability, numeric, and date-range predictions, and Metaculus's aggregation consistently scores well on calibration metrics.
It excels at science, technology, AI, and geopolitical questions, especially over long horizons, and is widely cited in research. Because there is no money at stake, it is less suited to casual speculation — but for serious forecasting and analysis it is among the best tools available.