Google Voice and Asterisk

[TheShniz]

...well said.

 

[Saqqara]

http://www.phonetag.com/ - Offers voicemail to text services. Not free, but they have been getting favorable reviews.

+1 for phonetag. My finicky boss has used them for over a year. Integrates well with PIAF; you don't have to use their voicemail, they give you an email address you can send a voice file to, and they will email text to the configured address.