How to export address book to mailchimp or CSV file?

I want to export specific address book groups to mailchimp from a clients Mac computer.

The client have version OS X Lion (10.7) and the Mac she has is faulty and will be scrapped soon. Therefore it is not feasible to upgrade it.

It would be perfect if I could use Chimport but it appears that I need OS X Mountain Lion to use Apple Mac Store to get it.

Alternative do you know any programs that can export to CSV?

Export your contacts as a VCARD bundle from Contacts.app and then import them into a gmail account which supports the VCARD format. Once in Gmail, you can then export them as a csv file.