Looking for knowledge expansion apps

Does anyone know some Android apps where you can find most of the important topics on a certain subject, like movies, history, geography and other stuff? In the arts category, good examples would be Artier and Google Arts and Culture.

I'm looking to casually expand my knowledge, eliminate boredom while commuting, and improve my chances at (local as well as global) quizzing championships. Areas in which many recommendations would be most appreciated are covered by WQC categories of Sport & Games, World and History.