To get you started you might want to implement a Google Voice like application. Though that sounds that might sound difficult, using Twilio it can easily be do

To get you started you might want to implement a Google Voice like application. Though that sounds that might sound difficult, using Twilio it can easily be done in a weekend. It will teach a lot about how to create Twilio applications plus it gives you the freedom that Google Voice lacks. For example I hated getting phone calls when I was in meetings. So I hooked my Twilio app into my Google Calendar API and bam, when I was in meeting Twilio would ask them to leave a message or press 5 if it was an emergency. Also greeting people by name when they call is pretty awesome.