Second Life is an online virtual world, developed and owned by the San Francisco-based firm Linden Lab and launched on June 23, 2003.
OpenSimulator is an open-source server platform for hosting virtual worlds and the Metaverse. It is largely compatible with the virtual world Second Life but compatibility is not a design goal.
IMVU is a 3D based social network using avatars, with user created rooms and high levels of avatar and room customisation. (Room creation requires the PC or Mac client).
In Facebook Horizon, not only can you explore the virtual world as it grows and changes, but you can discover all sorts of new things that interest and inspire you. Experience gravity defying, distance spanning, genre bending games of all types.
Miitomo is an app from Nintendo that brings out a side of you your friends have never seen before!Discontinued
Miitomo will end its service on May 9th, 2018: https://miitomo.com/en/notifications/180125/
The WhiteCore server is an OpenSim/Aurora-Sim derived project with heavy emphasis on supporting all users, increased technology focus, heavy emphasis on working with other developers, whether it be viewer based developers or server based developers, and a set of features around...This app doesn't have any features at the moment.
Discovery Grid is an Opensim-based virtual world. It operates much as Second Life does. Some of it's outstanding features are: Extremely low lag, large land masses available (up to the equiv of 64 SL sims!