"Jeyo Mobile Extender for Outlook adds mobile SMS messaging capabilities to your Outlook application by connecting your Outlook with a Windows Mobile Smartphone or Pocket PC Phone Edition device. It allows you to exchange text messages with other mobile phone users anywhere around the world directly from your Outlook and manage your SMS data with ease. With Jeyo Mobile Extender for Outlook, you will find using SMS from a PC as simple and easy as email."

This is a really nice piece of software and integrates very well into Outlook.

http://www.jeyo.com/products/JeyoMobileExtenderForOutlook.asp