Looks like TopXml.com has put up a nice System.Xml reference that shows the different XML classes in the System.Xml namespace along with their properties, methods, and some VB.NET sample code.   If you’re new to working with XML this should serve as a good starting point.

<shamelessPlug>I’d of course recommend checking out my site too at http://www.xmlforasp.net for .NET XML, ADO.NET, and Web Services code samples. J</shamelessPlug>