I have not found any decent conduits for the Address Book yet. So I've written a perl script that can convert Palm Desktop exported addresses to be readable by Apple's Address Book or Outlook Express (in OS 9). Unfortunately, it's still a manual procedure, but it works very well.
You can find the complete script over at my website.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020310232105575