In January 2014, we launched the rtc.debian.org service for the Debian community. An equivalent service has been in testing for the Fedora community at FedRTC.org.
Some key points about the Fedora service:
Create an RTC password and then log in. Other users can call you. It is federated, so people can also call from rtc.debian.org or from freephonebox.net.
You can use the RTC password to connect to the SIP proxy from many softphones, including Jitsi or Lumicall on Android.
The process to replicate the server for another domain is entirely described in the Real-Time Communications Quick Start Guide.
The FreeRTC mailing list is a great place to discuss any issues involving this site or free RTC in general.