Somehow, the MUD I grew up playing (MUME -- Multi Users in Middle Earth) is still alive and has a good amount of players. The game itself has served as inspiration for other worthy games (Ultima Online for example) and the PvP aspect is second to none. It is also an enormous world, covering Middle Earth from the dwarf fortresses of the Blue Mountains all the way east to the Misty Mountains, Lorien, and Fangorn.
www (dot) mume (dot) org