Telephony and voice APIs are one of the most active segments of the API and mashup world (our directory has 42 telephony-related APIs). For example, in the past week, two of the latest mashups in the directory use telephony APIs in innovative ways:
Ringful API Profile
Create rich voice and SMS mashups via simple RESTful API
Broadsoft Xtended API Profile
VoIP telephony services
Facebook API Profile
Social networking service
APIs, mashups and code. Because the world's your programmable oyster.
Executive Editor, ProgrammableWeb. Author, Map Scripting 101. Lover, APIs.