TinyBuild is giving away steam game key on their Facebook page such as Lovely Planet , Not The Robots , Boid and etc. You only get one game.
Go to TinyBuild , Like page , Fill out your Email address , Follow Twitter and then click on “Get Reward“.
Now, your key is ready. To redeem the key, Just open up your Steam client, and right click on the button “ADD A GAME” (in the lower left corner). Then select “Activate a product on Steam” and enter your key.