HubSpot - Grow Better With HubSpot: Software that's powerful, not overpowering. Seamlessly connect your data, teams, and customers on one CRM platform that grows with your business.
Twilio - Brings voice and messaging to your web and mobile applications.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Clockwork SMS - Clockwork is an Easy Text Message API. An SMS API for Developers. Build powerful apps and include SMS. Signup is free, Try it now.
Marketo - Marketo's powerful marketing automation software helps marketers master the art & science of digital marketing to engage customers and prospects.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates