AddressBook X LDAP provides a shared addressbook on your local network, without the burden of subscriptions. It is an iSync enabled application which transfers contacts from the AddressBook to a central LDAP directory. It also provides the ability to browse and search the directory. Multiple schema mappings are available and can be customized and extended to address individual needs. Currently, ABxLDAP Person (an extension to InetOrgPerson) is fully supported, but the Mozilla Schema and the basic InetOrgPerson are in development. Support for Active Directory is included as well.
Address Book Server allows you to share your contacts and calendar events with others connected to your network or over the Internet. Each participant synchronizes their contacts with the server hosted on your own system. Address Book Server supports the full Address Book and iCal schema. The server also provides a friendly Web interface and an iPhone client which let you access your contact details remotely.