Ok, before you look at this page, beware, that the powers that be do not approve of clients. Hmm, ok, "do not approve" is sort of speaking mildly. Basically, you may not use a client to send any commands to Valhalla. You are allowed to have the client display different info in different colors as you please, etc. As long as the client does not send commands to the MUD you are ok, though still frowned upon.
Note: Since I myself use a Linux/Unix client (Tf) I dont know too much about other systems. Actually I know absolutely squat. So send me your URL's or even zipped clients if they don't have a homepage.