Blizzard also is giving away a free in game Mechanospider mount for free if you play a Facebook game. I did it and it's not too bad but is currently experiencing some issues with a zillion people trying to play it.
https://teambuilder.heroesofthestorm.com/
If you are interested in checking out the Heroes of the Storm launch event archived feed.
https://www.youtube.com/watch?list=PL9WtwA1r0_TYrK0Nikr77uHZOJA96aryz&v=XNsxOaHCOr0

> Facebook game
Is this a game or just a "what character are you and your friends" quiz? I feel like I must be missing part of it.
Yeah, it's not really a game, but you know... you clicked things and it did the stuff.