Achaea, Dreams of Divine Lands
Achaea is a multi-user dungeon created by Iron Realms Entertainment. It is free to play with the option of purchasing 'credits' if you wish your character to advance faster. It is widely considered to be the last MUD that still has relevency in the MMOG world (with the possible exception of DragonRealms created by Simutronics). Unlike most others in the MMORPG vein, the economy, guilds, governments, cities, and everything else are run by the players. It is a restricted player killer MUD with strongly encouraged role playing.