Well, there is more than one. Each focuses on a different aspect of KDE. Some of them are for the developers, so they are not discussed in detail. The important lists are:
This is the main KDE mailing list for general discussions.
This list is used to announce new versions of KDE as well as new tools and applications.
This list is intented for users helping other users.
This is the list that deals with questions of look & feel and general user interface considerations.
This list is devoted to discussions about the KDE and Qt license issues.
For the complete list of mailing lists available, please refer to http://www.kde.org/contact.html.
Please note that it is not a good idea to ask questions which are already answered in this FAQ.