To start developing Phone Mashups:

Sign Up For a Free Developers Account With Ifbyphone
The first step in creating a Phone Mashup is obtaining an Ifbyphone account.  As a developer you are eligible for a completely free Phone Mashup Developer account.  You can learn more about the developer accounts and sign up at:

Open a Free Developer account including 100 monthly minutes for testing.

Dial into Ifbyphone and Learn About Call Routing
Phone Mashups that combine web sites and telephones begin when a user either initiates an action on a web site or calls an Ifbyphone telephone number.  If you are using a free Phone Mashup Developer account, then the telephone associated with your account is: (312) 252-1759

When prompted, enter the telephone number and pin you used to create your Phone Mashup Developer account.

Create Your First Voice Form (IVR)
Create a SurVo Form to collect some information.  For example, an order number, stock identifier, telephone number, customer information, etc. Use a  SurVo NetGet to send this information to your web application.  Your web application will recieve the data collected in the standard HTML request variable supported by your lanugage of choice.
Use this information to access data in your backend systems. Format a response for the caller as XML and include the name of the SurVo Voice Form used to read the response back to the caller.

Consider starting With a Click Instead of a Call
As an alternative to starting a Phone Mashup with a call into an Ifbyphone registered number, you can also start a Phone Mashup when a user clicks on an Ifbyphone Click-to-Call link or by using "curl" or your languages alternative to automatically place a phone call.

All documentation is available here.