Even though you can achieve this in several ways and with several different services and apps here is a guide how to sync you Address Book and iCal across multiple Macs via Dropbox.

Step 1 – Moving folders

First of all you have to move the following folders on the mac with the latest information in the databases into your Dropbox folder. (Replace “aidentailor” with your username) Navigate to “/Users/aidentailor/Library/Application Support/” and move the “AddressBook” folder to your Dropbox. Next navigate to “/Users/aidentailor/Library/” and move the “Calendars” folder to your Dropbox either.

Step 2 – Deleting folders

Delete the folders you moved to your Dropbox in the preceding step on the other mac.

Step 3 – Creating the symbolic links

Fire up the Terminal on either of the macs. It is not important on which one you start. Use the following Terminal commands to create the symbolic links to the corresponding folders:

“ln -s /Users/aidentailor/Dropbox/AddressBook/ /Users/aidentailor/Library/Application\ Support/AddressBook”

“ln -s /Users/aidentailor/Dropbox/Calendars/ /Users/aidentailor/Library/Calendars”

Remember to do this on each mac you want the data on.

Step 4 – Start the apps

Wait until the Dropbox is completely synced and then start up the apps.

Done