A lot -- almost all -- the talk about the new Silverlight technology from Microsoft has been about the "shiny", the ability to place hevyweight UI in the browser, and whether or not it will succeed in displacing Flash in a way that Java applets never managed to (But see also here).
Somewhat lost in all this has been what the technology is, especially in the 1.1 release, currently in alpha. Of course this isn't new -- remember all the "What is .Net?" thrashing about that took place when that technology was first announced -- all talk of web services and "Hailstorm" (MSFT Passport-on-steroids) -- and what we understand by the term now over 5 years down the line
The basis of the sliverlight technology is a portable version of the CLR (.Net) framework, referred to as the Core CLR. This is the bytecode engine and a slightly cut down set of APIs, though cut down in different ways to the .Net Compact framework -- it relies on APIs not present in that version.
And then comes the good bit.
The DLR has also appeared in the refactoring of IronPython -- and the recent 2.0 alpha release includes the
Microsoft.Scripting.dll that is at the heart of the DLR (though the current transition state is made apparent by there being a
Microsoft.Scripting.Vestigial.dll representing the remains of a first cut at refactoring to separate out what is now the DLR).
Two blog posts from one of the DLR developers (who's also been involved in Jython as well as IronPython) on how dynamic objects are being modelled in the CLR
and the start of a series on how compilation is handled (DLR Trees, part 1), which shows how it is complementing the LINQ features of C# 3
With IronPython and, soon, IronRuby as first class languages for the .Net framework there seems to be some hope that the .Net == C# (or, for those who want to join a sort of Coke vs Pepsi style debate, .Net == C# or VB) status quo may actually be coming to an end.