Neat little piece of free software from Microsoft: the SMS Sender. If you use Windows XP download the widget and type out and send SMS messages from your laptop. You’ll need some sort of connection with your GSM phone — infrared, Bluetooth, or cable. 
There are some limitations: It is not possible to retrieve messages from the cellular phone from the computer, and the application only supports standard SMS. Flash SMS and MMS are not supported. Other data such as ring tones and logos are not supported. Multiple SMS sending is not allowed.