Kevin Hoffman sent in an email regarding a flippin sweet project on CodePlex called CLINQ. It stands for continuous LINQ and is a .Net 3.5 extention. As changes occur in the source of your query, the result set is continuously re-evaluated to maintain consistency and accuracy. It was designed specifically to allow you to do declarative queries that auto-update for WPF binding in rich GUIs.
The project is at http://www.codeplex.com/clinq