Pottermore

[Marry The Night]

It's kind of like a companion to the Harry Potter books. You get to read parts of chapters (or even full chapters, not sure yet) from the books, and find bits of background information. That's all we really know for now, but there's bound to be more than just that. For example:

Spoiler for Pottermore Images:

As you can see, you can add other people as friends, collect potions and spells (not sure what you can do with them yet), go to your common room, etc.