Have you jailbroken your iPhone yet? If so, congratulations. You can now retrieve those voicemails left by your crazy ex-girlfriend and post it on the web for everyone to hear.
Here's how:
Jailbreak your iPhone (Duh). If you haven't yet, click on the instruction links for the Mac method and Windows method.
Connect the iPhone to your WiFi network (Settings -- WiFi), view the connection details and write the iPhone's IP address.
Using your favorite SFTP client, connect to your iPhone's IP address with username 'root' and 'alpine' as your password. If you have never used an FTP client, here are some you can use: FileZilla (Windows/Mac, Free), WinSCP (Windows, Free), Transmit (Mac, Paid), Fetch (Mac,Paid). Be sure to use SFTP and not FTP as your connection method.
Once connected, browse to the /private/var/mobile/Library/Voicemail/ directory. Once you are in there, you will see a list of .amr files. These are your voicemails and they can be played using QuickTime. Just transfer these files to your computer and you are set.