Since I have an Ipod Touch, I pretty much have to store my contacts in Mac OSX Address Book application so that they can sync to my device. Problem is, I also prefer Mozilla Thunderbird to handle my email. When I had looked in Sept 2007 ( when i got my Mac Pro ) there was no easy way to have my contacts in Address Book available to Thunderbird. In fact there was a bug open since 2003. Hoping this has been addressed (no pun intended), I did a quick Google and found that there is now a way... and actually there had been for a long time which either I missed or ignored before. A good summary of options to share address books with Thunderbird is here.
Since the release of Thunderbird 3 in 2008 never happened, I am left with the choice to install beta2, one of the nightlies, or build from scratch myself. The nightlies are found here.
I downloaded the May 30 nightly, but I have not decided to give it a whack yet. If I do I'll post back to let you know my experience.