One of the few things that the t809 does not do out of the box is Sync with with a Mac User's Address Book through iSync. Address Book itself can send the phone a vCard, but doing that 1 by 1 is hardly a workaround. After toying around a while, I re-discovered the useful little application "OnSync" from Onmadesoft. Even Onmadesoft wasn't certain it was possible, but, as I'll illustrate below, it's actually quite easy to sync the contacts from Address Book to your t809 using OnSync.
1) Get the Bluetooth settings ready on the t809 (Settings -> Bluetooth -> Turn Bluetooth On -> Select "On" AND Settings -> Bluetooth -> My Visibility -> Select "On").
2) Pair the t809 to your Mac through the Bluetooth Systems Preferance Pane (Bluetooth -> Devices Tab -> Select "Set Up New Device...")
3) Once pair, go grab OnSync ($12 through Kagi, but well worth it - plus, it's the only solution I've found).
4) After you open and register OnSync for the first time, the OnSync preferances will appear (if not, there's a menu option to access them).
5) In the "Mobile Device" tab of the OnSync preferences, choose "Samsung Phone SGH-D500 (and similar models)" for Mobile Type from the drop down list.
6) Next, select "Bluetooth" for the Connection Configuration and click the "Select mobile..." button. The default Bluetooth name for the t809 is "SAMSUNG SGH-T809." (NOTE: Using the "Serial over USB" does not seem to be possible, likely because the TransFlash memory card mounts as an external drive when the phone is plugged in via USB. Unmounting this, while keeping the USB cord plugged in, might solve that, as might disabling the mounting options on the phone.)
7) Click the "Test connection" button in the OnSync Preferances to finish setting up the connectivity with OnSync.
Voila! There are a number of other useful settings in the preferances, but none that will affect connectivity. Once you're done changes other preferances to your liking, save the preferances and the OnSync main window will be visible. Make sure to "Reload Numbers" to see the contacts stored on your phone and in Address Book. Let the syncing begin!