Cool, I've been looking for something like this:
via MacMegasite: Address-O-Sync is a new freeware utility ($5 donation suggested) which lets you synchronize your addressbooks via Rendezvous without using iSync or .Mac. [Mac Net Journal]
I'll have to give it a try when I get home. This plus a bluetooth dongle for my wife's iMac, and we might finally have reached address-book nirvana: one family address book, editable anywhere (2 phones, 1 palm, 2 Macs) and shared everywhere. Right now, all of my addresses and phone numbers are synced between my devices, but they aren't shared with my wife's, and her Mac and phone (T68i) don't talk to each other.
I swear, I'm never going back to non-synced phone address books. I'd buy a sync-able 5.8GHz home phone in an instant, if anyone made one.