Silverlight 4 is now available on the ECE site for both Windows Embedded Standard 2009 and Windows Embedded Standard 7.
"Silverlight is a powerful development platform for creating engaging, interactive user experiences for Web, desktop, and mobile applications when online or offline. Silverlight is a free plug-in, powered by the .NET framework and compatible with multiple browsers, devices and operating systems, bringing a new level of interactivity wherever the Web works."
For Standard 7 you can grab the feature from this ECE link "Microsoft Silverlight 4 for Windows Embedded Standard 7". This feature is for use with Windows Embedded Standard 7 compatible application templates available here.
For Standard 2009, Silverlight 4 is the only out-of-band feature in the November 2010 Feature Update for Windows Embedded Standard 2009.