Recently I got really curious about MUD(multi-user-dungeon) games, which are text adventures, like Zork, but are played by many users over the internet.
I think this is very fascinating, and I'm surprised that I wasn't aware of these before, so I thought it would be awesome to see some HN discussion about them.
I haven't been playing much recently, so it's hard to recommend any specific ones, but I was enjoying Sindome a while back. It's a Cyberpunk themed game that a lot of HN'ers might enjoy.