Catznip Second Life Viewer - Catznip is graphical client for Linden Lab's user created 3D virtual world, Second Life.
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.
Firestorm Viewer - Firestorm is to Virtual Worlds what Firefox and Google Chrome is to the Internet. We develop and distribute an open source viewer for accessing Virtual Worlds.
Vircadia - Vircadia is an open-source and decentralized real-time VR creation platform for university, enterprise, social, and OpenSim users.
VRChat - Create and play in virtual worlds with others
Kokua / Imprudence - Kokua is an open source viewer for Second Life and OpenSim-based virtual worlds.