Second Life - Second Life is a virtual reality platform where individuals interact in a virtual world. The software was developed in 2003 by Linden Labs. More than one million people now regularly use the software.
Planetbase - Planetbase is a strategy game where you guide a group of space settlers trying to establish an outpost in a remote planet.
Vircadia - Vircadia is an open-source and decentralized real-time VR creation platform for university, enterprise, social, and OpenSim users.
Banished - As always, Email support (at) shiningrocksoftware (dot) com if you have any issues. This will likely be the last update of Banished, except for any major bug fixes. The OSX and Linux versions development has stopped, and won't be released.
VRChat - Create and play in virtual worlds with others
Dwarf Fortress - Dwarf Fortress is a single-player fantasy game with two modes: fortress and adventure.