Craig Shoemaker's Polymorphic Podcast has a nice two-part interview with fellow “geek with blog” Miguel Castro about “Architecting for Extensibility”.
You can hear the interview here.
If you're not familiar with Craig's podcast, check it out. It's a while between shows sometimes (hey, we can't expect everyone to be Carl Franklin), but they're always worthwhile.
Craig is also co-author of a new book: Beginning Ajax With ASP.NET.