Asmodee Digital (Steam Publisher)

The French publisher of board games also has a Steam presence, with very many of their games available to play, for a price.

TableTop Simulator

A physics engine designed to allow players to sit around a virtual tabletop and play games.

Some free games, but most are paid DLC, and all players need to have bought the relevant game.

TableTopia

Another physics engine that allows playing at a virtual tabletop to play games.

Many free games, but for many others you will need to pay for the game or a subscription.