The Treo 600 on its own is unable to send contacts via SMS. After searching this forum, I found that SMSAddress http://www.hexlet.com/products/smsaddress/ supports this function. Hexlet says that SMSAddress enables the Treo 180 and Treo 270 to exchange (send and receive) contacts via SMS. It does not work on the Treo 300.

But the good news is that it works on the Treo 600. I am wondering if there are other similar programs out there?