Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Kannel - Open Source WAP and SMS Gateway
Twilio - Brings voice and messaging to your web and mobile applications.
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
Atomic SMS Sender - Free bulk SMS software to send bulk text messages from PC
KAPSYSTEM - KAP Computer Solutions Pvt. Ltd.,