VCFConvert is an online resource that will allow you to upload your exported OSX address book contacts (vCard format), and will convert them to either an LDIF or CSV file which can easily be imported into your Thunderbird Address book. If you are unsure about the privacy of sending your Address Book contacts to this website, you can also download the PHP script which will do the work for you. Just host the files on your own server and convert.
★ Mac OSX Address Book to Thunderbird 3 Contacts Converter (vCard to CSV or LDIF)
Posted on December 19, 2009