I'm giving a speech on Master Pages Tips and Tricks to the Capital Area .NET User Group in Virginia on behalf of INETA and Interface Technical Training.  Those interested in downloading the code samples and slides for the presentation can find them here:

 http://www.xmlforasp.net/CodeBank/Download/Blog/MasterPageTipsAndTricks.zip

 Topics covered include:

• Handling paths in Master Pages  
• Tips on handling nested Master Pages in design-view
• Accessing controls within Master Pages from Content Pages using the MasterType directive
• Providing consistency across multiple Master Pages using abstraction and inheritance
• Dynamically assigning Master Pages at runtime
• Assigning Master Pages dynamically to all pages in a Website using an HttpModule
• Sharing Master Pages across IIS applications

If you're interested in reading more about Master Pages tips and tricks check out the following blog posts written by Scott Guthrie and K. Scott Allen.  I'll be discussing several of the tips these two have written about at the meeting.

http://weblogs.asp.net/scottgu/archive/2005/11/11/430382.aspx
http://www.odetocode.com/Articles/450.aspx