WPF
An auto-complete TextBox is an awesome feature that just about any application can use from time to time. Whatever saves keystrokes and clicks is a good thing. Here's how to make a pretty simple one using Linq and WPF.
An old "article" I wrote a long time ago (9 months) on how to change the SelectedItem in a TreeView (assuming you're using and ObjectDataSource) AND have the user interface update as well. Not the greatest stuff in the world here...but...it works.