This week Microsoft unveiled the August Preview of Expression Blend 2. Version 2 of Expression Blend enables users to create Silverlight applications. In addition, the Silverlight 1.0 Release Candidate is also available for download.
Download the Expression Blend 2 August Preview here: http://www.microsoft.com/expression/products/download.aspx?key=blend2preview
Download the Silverlight 1.0 Release Candidate here: http://www.microsoft.com/silverlight/downloads.aspx