With the release of Leopard on Mac, it seems that receiving and sending messages from Address Book has been removed. Worry not though, you can still do this with the emitSMS Widget.
The widget only works with certain Bluetooth mobile phones from particular brands like Nokia or Motorola, so you first need to check in the drop down menu that your model is supported. Once you've found your model you'll have to ensure that the Bluetooth connection is working. This can be a little tricky.
Sending an SMS is a breeze. Use the box to type in your message. On the flip side you can set the widget so it allows you to write longer messages. Instead of typing in your contact's phone number, emitSMS syncs up with your Mac's Address Book to quickly access your contacts' phone numbers. This works really well and makes sending SMS much easier. There are a few other useful features on the flip side of the widget, like being able to get a delivery receipt or storing messages. Our only real pet peeve would have to be the "send" button itself, which is a little small.
emitSMS is a very useful widget to send SMS via Bluetooth from your Dashboard.