GotVoice is a wonderful service that will convert your voicemail messages on your cell phone or home phone and send them to you through your email. It will convert the messages to a MP3 format and deliver them straight to your inbox for your listening pleasure.
The basic service that they offer is FREE, but if you want it to check for voicemails more times throughout the day then they offer some premium services. The $5 per month service will check for messages more than the free service does and the $10 per month will check for messages more than the $5 service does. If you pay $10 per month for the service they will also give you an RSS feed for your voicemails so that it is even easier for you to keep track of new voicemails.