As mentioned by akalsey, Tropo could be a good option if you wish to use a hoste...

nimish79 on June 3, 2011 | parent | context | favorite | on: Plivo - an opensource alternative to Twilio

As mentioned by akalsey, Tropo could be a good option if you wish to use a hosted service. If you wish to have greater control and host things at your end and use your own carriers and phone numbers, then Plivo is the way to go.