Hi,
I have another example of developing a DSL in my functional-programming book. I'm mentioning this because the source code is available for free here: [link:www.functional-programming.net]

In chapter 15, there are two examples. The first one shows how to create a DSL for writing animations, so you can for example write something like this to create a solar system simulation:

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let sun   = circle (forever Brushes.Goldenrod) 100.0f.forever
let earth = circle (forever Brushes.SteelBlue) 50.0f.forever
let mars  = circle (forever Brushes.Chocolate) 40.0f.forever
let moon  = circle (forever Brushes.DimGray)   20.0f.forever

let planets = 
   sun -- rotate 120.0f 1.3f 
            (earth -- rotate 50.0f 12.0f moon)
       -- rotate 160.0f 0.7f mars
  
af.Animation <- faster 0.2f planets

Another example, which is a lot simpler demonstrates how to model financial contracts. I just checked the source code and it seems to work fine with May 2009 CTP. I don't yet have project files for Visual Studio 2010, but I'm planing to add them soon.