Have you heard of BTM?
It's a Minecraft conference done in-game.
There's a Minecraft server on which the convention center is built, with lecture rooms, booths, etc. Slides are shown on text-mode displays of in-game computers. Voice chat is done with Mumble with positional audio, and lecture-room-specific channels for listening to talks. Questions are asked on in-game chat.
@Wolf480pl I haven't, but that's pretty awesome!
Welcome to your niu world ! We are a cute and loving international community Ｏ(≧▽≦)Ｏ !