Materia Magica is by far one of the best games I have encountered on the web. The creator of this IEN, termed by many as "Vass", and the Immortals are constantly adding new equipment and skills/spells. Just this year, many new areas have been added (I can count about five).
This unique game also has a good questing and levelling system (you can choose four of thirteen different classes, plus the special Archon class after you have completed your first four), over 70 clans, and many more great features.
Materia Magica also has a beautiful web page crammed with useful information. From there, you can access all the help files, view the atlas and maps of cities, contact the Imms, and post on a message board visited frequently by many players from around the world. There is also a FAQ section and a registry section (where players can post information about their characters and about themselves).
So, if you are looking for another cool game to play on your free time, (not one of those MUDs that get too small and too boring), Materia Magica is a must-try. (Did I mention, role-playing is encouraged. :P)