Microsoft just released Silverlight 2 with all developers and designer tools:
- Microsoft Silverlight 2 SDK
- Expression Blend 2 SP1
- Silverlight Tools for Visual Studio 2008 SP1
- Deep Zoom Composer
- Silverlight 2 Developer Runtime (Windows)
- Silverlight 2 Developer Runtime (Mac)
And the surprise is that there is also some tools for Eclipse: http://www.eclipse4sl.org/
Read more on the Silverlight web site and on Tim Heuer blog.