Cockatrice - Cockatrice is an open-source, multiplatform program for playing tabletop card games over a network.
XMage - XMage allows you to play Magic against one or more online players or computer opponents.
Hearthstone - Pick up your cards and throw down the gauntlet!
Wagic - Wagic the Homebrew. Contribute to WagicProject/wagic development by creating an account on GitHub.
OCTGN - OCTGN (Online Card and Tabletop Gaming Network) is a virtual table top with an integrated player lobby and chat system that supports custom card and board games.
Magic: The Gathering - The classic card-trading strategy game brought to the PC.