Visual Studio 2008 SP1 用 Microsoft® Silverlight™ 3 Tools
http://www.microsoft.com/downloads/ja-jp/details.aspx?FamilyID=9442B0F2-7465-417A-88F3-5E7B5409E9DD
http://download.microsoft.com/download/B/C/4/BC4E1E6A-047F-498B-B6A5-B15CAE9DD3C8/Silverlight3_Tools.exe