I've been playing NannyMUD now for over 6 years, and have to say that my enjoyment of it has only just begun to wane due to the lack of active 'role playing'. As a game though, it's brilliant and I have enjoyed many many hours online meeting people, fighting monsters and questing. It's fairly newbie friendly depending on who is approached and generally which guild they play in. A number of guilds are available, some more imaginative than others, and sadly some closed down due to hacking attempts by now banished wizards. Guilds include the Noble Knights, Mad killing Khornes, Healing Monks, Evil Cthulhu, Naturalistic Druids, Vampires and Chefs. All guilds are of varying degrees of fun to play depending on an individual's knowledge of the MUD. It is essential to get into a guild though as soon as you can, as it vastly increases the gaming experience and comradery felt in most of the guilds.
Role-playing in a non-regulated sense does not, sadly, exist to a great extent, however it is encouraged to different degrees depending on which Guild you are in.
The MUD as a whole is massive, and there are rooms which to this day have not been discovered. Hours of blood, sweat and tears go into building areas, quests and monsters for players to discover and enjoy, and the imagination of some of the areas can blow your mind... humourous, scary, beautiful descriptions are all found in this MUD.
And if the room descriptions and quests aren't enough for you, then you can always join the numerous clubs available, from the worship of the great designer and 'god' of Nanny, Mats, to the Flatworlders club, the Monty-Python-esque lumberjacks club to more recent additions, The Spammers club, Snowball club, Tag and Chess - all interactive games which any can take part when breaking from a taxing dragon-slaying quest.
It is in this way, that great friendships and more can be formed and regular parties are held generally in the US, in Sweden or in the UK. At least one a year when MUDders from round the world unite in Sweden to celebrate the birthday of Nanny. I, for one, love Nanny, the game is a secondary reason for my spending so much time there as old friendships are reinforced and new ones made with each visit.