Just saw a posting that eclipse4SL - the Eclipse tools for Silverlight project is available. It is an eclipse plug-in that enables Eclipse developers to use the Eclipse IDE to create applications that run on the Microsoft Silverlight runtime platform.
The purpose of this project is the creation of open source tools integrated with the Eclipse development platform that enable Java developers to use the Eclipse platform to create applications that run on the Microsoft Silverlight runtime platform. Specifically, the project will be an Eclipse plug-in that works with the Eclipse Integrated Development Environment (IDE) and Eclipse Rich Client Platform (RCP) to provide both a Silverlight development environment and greater interoperability between Silverlight and Java, to facilitate the integration of Silverlight-based applications into Java-based web sites and services. The project has been submitted to the Eclipse Foundation and released as an open Eclipse project.