A ringback tone is the ringing that is heard by the person who dialed the phone call prior to the call being answered at the receiving end.
Ringback Monkey v1.2 is open-source software that sends ringback tones to your phone for free. You also may upload ringback tones from your computer. Ringback Money works will all major carriers including Verizon Wireless, Cingular, Sprint, Virgin Mobile, Alltel, and more! Download and follow the easy instructions.