I'm a fan of Backpack and use it extensively for managing any number of different things. I'm also a fan of Packrat which is great for bringing Backpack onto planes with me. One of the great features of Backpack is the ability to add content by sending an email any Backpack page. Every page has a unique address and Backpack is able to understand the structure of special emails to add them to the right section of the page. It is uber-cool, but you can easily have 50 or more Backpack pages and that's a lot of addresses. I wish I could have these in my email address book. Enter Packrat. The most recent version of Packrat added AppleScript support. I had asked the author to add a special feature to export addresses, but instead we got AppleScript support so now it's easily done with a few lines of script.
Grab the Packrat Email Address Export AppleScript I created and you can easily create a text file that you can import to the address book of whatever mail client you prefer. Note that I've tested this only to create an export that will work with GMail. There is a comment in the script for the specific write line that you can change to move the fields around.
PS: Yes I could have used
curl and some script magic to get this done without PackRat, but when I have a great object model already exposed why not just make it easy.