A long-time player of medieval fantasy MUDs, I am happy to give a shameless player plug of the newest to receive my attention, the world of Eaxia Online.  

The world is continually changing, with a brand new combat system coming out soon!  Play for free if you like, or for a few dollars more enjoy various perks like extra characters, player homes, and a free item/home furniture alteration each month.

If a dymanic role-playing environment is what you are looking for, look no futher than Eaxia Online.