Here's a non-exhaustive list of interesting posts/articles on the DLR. If you find something that's not listed, but should be, add a comment below and we'll add it to the list.

DLR

Discussion/overview of the DLR
*http://gotnet.biz/Blog/post/The-DLR-is-the-Language-of-Languages.aspx
wikipedia article on DLR
*http://en.wikipedia.org/wiki/Dynamic_Language_Runtime
DLR on mono?!
*http://forum.xda-developers.com/showthread.php?t=465590

Expression Trees

Getting information about types, objects, properties, values, etc...
*http://blogs.msdn.com/csharpfaq/archive/2010/03/11/how-can-i-get-objects-and-property-values-from-expression-trees.aspx
*http://blogs.msdn.com/csharpfaq/archive/2010/01/06/getting-information-about-objects-types-and-members-with-expression-trees.aspx
Generating dynamic methods
*http://blogs.msdn.com/csharpfaq/archive/2009/09/14/generating-dynamic-methods-with-expression-trees-in-visual-studio-2010.aspx
Debugging expression trees
*http://blogs.msdn.com/csharpfaq/archive/2009/11/19/debugging-expression-trees-in-visual-studio-2010.aspx
Using blocks
*http://blogs.msdn.com/mitsu/archive/2010/03/02/c-4-expressions-blocks-part-i.aspx

DynamicObject

Good intro article
*http://blogs.msdn.com/csharpfaq/archive/2009/10/19/dynamic-in-c-4-0-creating-wrappers-with-dynamicobject.aspx#comments
More good examples
*http://blogs.msdn.com/csharpfaq/archive/2009/10/19/dynamic-in-c-4-0-creating-wrappers-with-dynamicobject.aspx

ExpandoObject

Good intro blog on this
*http://blogs.msdn.com/csharpfaq/archive/2009/10/01/dynamic-in-c-4-0-introducing-the-expandoobject.aspx
Cool article on more advanced topics
*http://reedcopsey.com/2009/11/06/unusual-uses-of-expandoobject-in-c-4/
Interesting article on an "elasticobject"
*http://amazedsaint.blogspot.com/2010/02/introducing-elasticobject-for-net-40.html

C# Dynamic

Good video on dynamic and how it works.
*http://channel9.msdn.com/posts/CharlieCalvert/CSharp-4-Dynamic-with-Chris-Burrows-and-Sam-Ng/