While looking around for something to match EasyB a BDD framework built in Java\Groovy I came across this Boo based DSL for MSpec. Dynamic languages (the meta programming abilities in particular) make for a far easier english reading test than static languages can create and it's good to see what Boo is opening up on the CLR.
SpecFlow was a new one on me with a style of BDD that is a lot like Cucumber, more details in this post.
Sean Foy talks about his implementation of AndAnd (following the example of Ruby's Object#AndAnd) using first LINQ AST and then later Monads. The discussion around Monads I found quite interesting.