I have probably learned the most about XAML and the Windows Presentation Foundation (WPF formerly Avalon) by going through the Hands-On-Labs. Most of these originated at the PDC from last year. Any how, they are a great way to get familiar with XAML and they were much needed since the schema for XAML has changed significantly since these were originally released. If you have an interest in learning XAML (and you should), I recommend you check them out.
WPF Hands-On-Labs
Read the complete post at http://www.dotnettipoftheday.com/blog.aspx?id=251