Miranda NG - Miranda NG is a successor of a popular multi-protocol instant messaging client for Windows - Miranda IM. Very light on system resources and extremely fast.
Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
Pinger - Pinger lets you text and talk free with the people you care about most, anywhere on the planet.
Kannel - Open Source WAP and SMS Gateway
Tencent QQ - Tencent QQ is a free instant messaging computer program developed by the Chinese company Tencent Holdings Limited.
Bulk SMS Services - Sending Bulk SMS to the customers will engage the customers with your business and new offers.