Hearts of Iron is a series of World War II grand strategy games by Paradox Interactive.
Hearts of Iron: The Card Game is a free-to-play TCG spinoff. It's still about resource management and World War II, but it's a card game now.
Those of you who dwell in the chatroom may recall me mentioning I was quite interested in this game back when Paradox announced it. Well, it's playable now, and I'm still quite interested. It's entirely browser-based, too, so as long as your Web-browsing device of choice can handle Flash, you can play.
Let's play this, guys. It's free and it looks like it'll be pretty fun.