Busy day. A new open source project “Eclipse Tools for Silverlight” - http://www.eclipse4sl.org/ has just been announced. Full details can be found here. http://www.microsoft.com/presspass/press/2008/oct08/10-13Silverlight2PR.mspx .
This will bring the Silverlight RIA development experience to Eclipse developers and solve interoperability challenges between Silverlight and the Java middleware services that use REST, SOAP, JSON and other standards.
I am not sure that this would have happened without some really strong support from the Eclipse foundation ( http://dev.eclipse.org/blogs/mike/2008/10/13/interesting-times-indeed/ )