I was just reading Scott Guthries blog post about silverlight 2.0 and I came across a section discussing how Silverlight will be able to do cross domain calls. I have been very curious how they were planning on solving this one without risking the security of silverlight.
It turns out that all you need on the remote domain is an XML policy file that will allow applications to call your domain directly. It seems that this is how flash has been doing it for a while now and silverlight 2.0 will also respect flash policy files.