Silverlight 4 is the latest permutation of Silverlight, the release of this coincides with the release of Visual Studio 2010,
and also .NET 4, of which Silverlight shares a little of it's XAML magic.
Here is the classic Hello World example brought to Silverlight with Visual Basic and Visual Web Developer 2010 Express Edition.
www.cespage.com/silverlight/sl4tut1.html
Demo