In the Mindsharp Summit for SharePoint Developers, I teach students how to exploit Windows SharePoint Services (WSS) and SharePoint Portal Server (SPS). But before we delve into things like creating custom Web Parts, Web Part properties, Web Part Tool Parts, and Event Sinks; we explore how SharePoint initializes sites using the underlying Site Definitions in the 60 Hive. I like to say that the 60 Hive is the starting place for everything SharePoint. At the very least, it is the basic building block upon which everything else in SharePoint is built.
I use the following image to explain how the 60 Hive is structured:

The Site Definitions are found in the subdirectories on the right.
Consequently, I've decided to name my blog: Todd Bleeker’s 60 Hive - my starting place for everything SharePoint. I hope to help other people understand aspects of SharePoint that I've had the opportunity to explore.