Stramit wrote a real good blog post on SharePoint 2007 TreeView navigation. He is used our good friend Reflector to dive into the SPTreeView and SPHierarchyDataSourceControl to find out what you can accomplish with the SharePoint TreeView navigation controls. He explains how to create a custom masterpage where he modifies the properties of the SPHierarchyDataSourceControl to configure what to display in the TreeView, like Lists, Document Libraries, Sub webs. He also explains how to set to root context from where navigation is displayed to the root web of the site collection by using custom server side script in the masterpage. But hé, you can’t use serverside code in your masterpage I hear you think… wrong!! With some tricks you can get it working. Read Stramits blog post if you are into the navigation game. Good work Stramit!
Some of my earlier SharePoint navigation related posts: