SynSpace is a free multiplayer spacewars game for 8 players per channel. Players drop in on an ongoing battle as they feel like it. Powerups provide ships with additional weapons and effects. Space is filled with obstacles and zones. These are provided by maps selected by the channel moderator. You can also make new maps and share them with your friends. Play team or free for all, capture the flag or simple melee battle.
This game is part of the Synthetic Reality "Arcadia" family of games. (http://www.synthetic-reality.com/arcadia.htm) Players add additional channels at will using the integrated MIX server. Arcadia itself provides all networking support, in addition to text chat, voice chat, web browsing, and a parallel existence park environment for serenity, duck-feeding, and paintball while you wait for other players to show up. Arcadia allows you to create a personal identity with which to expose your current emotional state, and maintain a diary of other players you have met in the game.