SIP2SIP provides free server support for SIP signaling, RTP media (Audio and Video), NAT Traversal (including ICE), MSRP media (IM and File Transfers), Presence and XCAP (SIMPLE) and Multiparty Conferencing with wideband Audio, IM, File Transfers and Screen Sharing.
This service runs on SIP Thor platform. The SIP accounts is reachable from any open network and you establish session to SIP and XMPP addresses or phone numbers. You can use multiple devices located on the public Internet or behind NAT routers.
To register your SIP account go to http://sip2sip.info