I just realized that in all the excitement and business that is coming home from TechEd I didn't blog about my last day there.

I only made it to 1 session. That was WEB 327 - Best Practices for UI with ASP .NET 2.0.
Using XHTML and CSS will make your pages easier to create and maintain.
ContentPlaceHolder goes onthe master page, ContentControl goes on the detail page.
When you declare the master page in the web.config you loose some intellisense support and some designer support.
Change the master page file in the preinit event.
Use themes to change visual appearance, use master pages to change content.
You can use a menu with only static display, images, and CSS to make a tab bar.
Themes can be set a t the page or web.config level. You can swap the theme in the preinit event.
StyleSheetThemes show up in the designer, themes do not.
csszengarden.com is a good example of changing display using CSS