Kldap is a graphical LDAP client written for KDE. Kldap has a nice interface and is able to show all the information tree stored on your Directory. You can check some screenshots from the application and download it at: http://www.mountpoint.ch/oliver/kldap/
KDirAdm is a LDAP Directory management tool written for the KDE Desktop Environment version 2 or later. It aims to provide all of the functionality of most commercial directory management tools: http://www.carillonis.com/kdiradm/
Directory Administrator is the most widely used GNOME application for managing UNIX users and groups on LDAP directory servers. Directory administrator allows you to create and delete users and groups, and manage your users associated address book information, per-server access controls and Sendmail mail routing: http://diradmin.open-it.org/index.php
GQ is another graphical LDAP client with a simpler interface. It was written for GNOME. It also runs under KDE, the same way Kldap runs under GNOME. The address for downloading and getting more information is: http://biot.com/gq/
LDAP Browser/Editor: This tool is fantastic, it has complete administrative and browsing funcionalities. Check it out: Ldap Browser.