Is there some web front-end to administer LDAP servers, in a similar way as you can use phpMySQLAdmin to administer DBs?
I think you mean phpLDAPAdmin.
It's not a web front-end, but I like Softerra's LDAP browser. It comes in free and paid-for versions, although I've only ever needed the free one.
What kind of LDAP are you trying to manage - OpenLDAP, eDirectory, something more exotic? If there's a management tool that the vendor provides with it, you may be better off using that.