Address Book cards, one of the best ways to organize contact data on your Mac OS X. If you are active on Facebook, you can now use AddressBookSync, a free application for Mac OS X, which can be used to sync the data of your Facebook friends onto your Mac OS X address book.
There are more advantages if you have a phone that supports Address Book Synchronization. You can sync up profile picture data, with contacts on your phone, which will result in profile pic showing up when you get a call from any of your friend. You can also use the same to synchronize birthday dates and other local information about them on to your Address book.
However, since Facebook’s TOS does not allow access to it’s users e-mail id’s and phone numbers, you won’t be able to sync their e-mail id’s and phone numbers.
A very handy tool if you have a lot of friends on Facebook and you want to keep your contacts updated with their latest pictures and other information which Facebook gives access to.
Facebook is a good start, but I’m sure this can be further improved for other social networking sites as well.