Have a robot call your friends and recite song lyrics. Try it!
First, you'll need a place to host the app. Heroku is a good choice.
Next, get a Tropo account and create an application.
Set the voice URL of the application to http://yourhost.com/calls/initiate.json
Set your Tropo outbound voice token to TROPO_VOICE_TOKEN environment variable.
You should be good to go!