Our MVP's rock. In addition to the work they do supporting and promoting our products, as well as providing feedback to us on what we're doing, they've been implementing a set of additional XML-centric components for the .Net Framework, collectivly called the MVP.Xml library. Oleg Tkachenko just recently announced that the first release of this library is now available for download and includes support for XInclude and XPointer.
You can find out more information at the the MVP.Xml Project Website.
MSDN XML Dev Center Content Strategist