ZYB has social networking aspect around your mobile contacts. Mobile contacts might be close friends, family or the ones you know very well so it makes sens to have social network around them. Once you login to ZYB you could search for the users in your contact list if they are already in ZYB you can add them to your contact list.
ZYB is launching a ZYB phonebook application in the second quarter of 2008 that looks promising. It allows you to see your friends physical location, see the timezone of your friends to make a call. Allows you to receive life streams of your contacts from Facebook, Twitter etc when you are away from your computer.
ZYB is free to use and is available in major European languages apart from English.