I learned XSL in 30 minutes by going to www.w3schools.com they had a tutorial that went over the basics. Very cool. They have other tutorial son the other parts of it that I think are probably just as easy to understand Mark
For books I have found two that I have worked with the first XML Bible by Eliotte Rusty Harold is a pretty good reference. The second was Java and Xml by Brett McLaughlin. This book is programming oriented and I thought was a good start to writing code to parse/manipulate/output XML. It covers both DOM and SAX. As far as websites .... there a re a lot of them out there. I started at apache.org though (xml.apache.org) there you can download xerces/xalan and each comes with examples and samples to look through.
subject: How to start learning XML, XSL, DOM and SAX?