Metaforecast is a search engine for probabilities.

Given a query, it searches for relevant questions in various prediction markets and forecasting platforms (namely CSET-foretell, Elicit, Foretold, Good Judgment, Good Judgment Open, Guesstimate, GiveWell & OpenPhilanthropy blogposts as of early 2021, Hypermind, Ladbrokes, Metaculus, Omen, Polymarket, PredictIt, Smarkets, William Hill, and Michael Aird's database of existential risk estimates).