[patio11]

They have a full voicemail & whatever thing with a web console for administration, as an OSS app, if you like that.

http://www.openvbx.org/

I don't actually use it, but I like the basic idea: spend your expensive programming time on places where your unique contribution adds value to the business. Common infrastructure code, on the other hand, is like a web server: download the appropriate bit of OSS, drop it in, go back to doing valuable work.

(I do my voicemail with a Twimlet, which is a less powerful version of the same idea: here's the minimum viable voicemail-to-email script, just copy/paste this URL into your config and you're good to go.)

[runT1ME]

Just know that even though the front end is Open source (and looking pretty awesome might I add), the backend telco stuff is tied to twilio which means you'll be paying their usage fees.

Unlike other open source solutions such as Asterisk or Freeswitch (which both suck in their own ways) where you can buy your own VoIP trunking/termination service from any number of companies and negotiate your own pricing.

Tropo has Twilio like functionality and some out of the box features for pbx-ing, but they allow you to either run hosted, or if I'm not mistaken, purchase their own backend telco engine and run in your own network with your own trunking provider.