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.
Unity - The multiplatform game creation tools for everyone.
Vircadia - Vircadia is an open-source and decentralized real-time VR creation platform for university, enterprise, social, and OpenSim users.
Struckd - 3D Game Creator - Struckd is the next-generation gaming platform for user created content where people of all ages...
VRChat - Create and play in virtual worlds with others
Reality Factory - Reality Factory is a free suite of game development tools for building 3D games.