Suggestion for a simple LDAP server and client
Solution 1:
OpenLDAP for the server. It is pretty much the standard. I have used it as a replacement for Active Directory for User/Computer domain authentication.
For a GUI, I prefer a cross-platform client. I use various OSes. I used to use LDAP Browser (Java) but it was hosted at a University page and is no longer available.
JXplorer is an option for a GUI. It is also in JAVA. You can also use LDAP Admin
If you need documentation, there are several documents out on the web that describe step by step. I highly recommend finding one for your specific OS distribution.
I also recommend reading the "LDAP Linux HOWTO" from tldp
Solution 2:
Another option exists for both server and client: Apache Directory (http://directory.apache.org). They also have an Eclipse RCP based browser/editor which seems very, very nice.
Solution 3:
A good LDAP option is OpenLDAP, there is plenty of information out there on setting this up. As far as a client/manager I would recommend a web based one named phpLDAPadmin (PLA) and a desktop client that works well in windows would probably be one offered by Softerra. I typically use either a linux or unix client by the name of ldapbrowser (lbe).