What software do admins use to administer ldap directories. I have found two pieces of software that I use regularly.
The first is ldap account manager. This works well for getting your directory up and going. Once you create the root of the directory as well as your administrative user, LAM (ldap account manager) will create the necessary directory structure for allowing linux server to authenticate against the directory as well as Samba. You can create templates in LAM for adding users and groups which makes adding users easy. In a template you can specify specific attributes to apply to a new user such as group membership, address, etc. There is also a schema browser that is really just phpldapadmin.
For modifying users I find LAM to be a bit clunky so the second app I use luma. Luma is a client app written in python that works for linux and freebsd. I find this useful for quick user management such as changing groups.