WP Comments Notifier is a open source application written in QT/C++ for Linux and Windows, which will allow you to manage new comments and reply to them from your desktop. In addition to that, it will also allow you to edit, spam or delete the comments.
More at: http://weblogtoolscollection.com/archives/2010/03/08/manage-comments-from-your-windows-or-linux-desktop/