Manage Outage Notifications?

What are people using to manage / send their outage notifications? We're currently using a mostly manual process to identify customers that need to be aware of an outage and send out e-mail at $dayjob. Looking for a way to automate it more. I'd prefer something open source, but that's not a requirement.

Thanks

Hi Shawn,

I've been very impressed lately with https://www.pagerduty.com/

Nice control of a staff rotation. Distribution to multiple groups
depending on area of responsibility. Very customizable escalation.
Android and iPhone apps in addition to SMS and voice call support.

Regards,
Bill Herrin