In the latest snapshot, Mojang released a preview version for a new feature called Minecraft Realms. Basically, it will eventually become Mojang's own set of multiplayer servers, and possibly a way to easily rent or buy servers from them. Due to it dealing with world wide servers, Mojang only released the feature to a small number of users, each one chosen randomly.
So, my question is to those who have been playing the snapshots, who has gotten the feature? If you have it, there should be a button in the main menu saying "Minecraft Realms". If you don't, the button won't be available.
If you want more info about the feature, Sethbling has made a video about it. Not much more than I said, but it gives a visual reference, and a short preview. The explanation last for about half of the video.