Esmska is a cross-platform application for sending GSM SMS over the Internet.
It uses publicly available web gateways and sends messages through them.  This
way it can be much more comfortable than using a web browser or a mobile phone.

Features:
 * Send SMS through various gateways (local or international, free or paid)
 * Supports all common operating systems (Linux, Windows, Mac OS, etc.)
 * Free, under open-source licence GNU AGPL3+
 * Import contacts from vCard files or third-party programs (DreamCom)
 * Send SMS to multiple recipients at once
 * History of sent messages
 * Pluggable gateway system - easy to provide support for more gateways
   directly by users
 * Extensive possibilities of changing appearance
 * Many other planned features

WWW: http://esmska.googlecode.com