Backing up contacts to Macbook Pro

I must preface this question by saying it is probably incredibly noobish, but how can I back up my contacts to my computer and make them usable with the new messages app on ML? I have an old backup already on there but because I often restore my jailbroken iPhone and re-load my contacts onto it I've gotta know how to keep the backup on my computer up to date. I'd really appreciate any help you guys may have to offer!

-Jake