We're not sure if Paris used this particular service, but by using the Jajah web interface you can "hack" into someone else's voicemail. Intrigued? Good. Maybe this will get Cingular to fix their phone system.
How it works: Go to Jajah, enter in the number you want to "hack" as both the recipient and the caller. Then, call that person with Jajah. As long as the person doesn't pick up and the call goes to voicemail, you have access to whatever messages are there. Oh, and we think they need to have turned off the PIN authentication too.
This also works with VoIP software/services like Asterisk where you can program in your own caller ID.