Metropolis Metaversum - The Metropolis-Grid offers a free Membership and virtual Worlds, free of any charge. Citizens can connect their own simulators to the grid, for free! Everything is possible at Metropolis!
Linking your region to this grid is fairly easy, they provide their own pre-configured OpenSim. Just find coordinates that are empty on the map, then boot up (and setup) OpenSim as normal. A note of caution about this grid, I'm not sure if this is normal for them or if we just caught them on an off day, but apparently during our test link we managed to rez on top of another region that showed as empty on their grid map. On other grids, this results in an error & immediate exit, on this grid it apparently allowed it; however we experienced 3 FPS sim side (55 FPS is our usual) and quickly disconnected. The next day we received a strongly worded email from the grid admin demanding we disconnect our region and stop "intentionally" disrupting their network - our region had been reconnected to OSGrid for about 36hrs at that point & we were connected to Metro for less than 15 minutes when we did the test link. Be sure to check the In-World Map BEFORE you connect a region, do not trust the web based maps on ANY grid, they usually do not show varregions that can take up several squares but will still show empty.