Some days ago Ezequiel Glinsky sended me a link to Microsoft Live Relay Service. From that moment on I fascinated with this new technology that makes possible the communication among Web Services that are behind firewalls or NAT’s. It is also very interesting the Mictosoft Live Labs STS, a public Secure Token Service that uses Windows CardSpace.
To get start with this service go to http://relay.labs.live.com/GettingStarted.aspx.