So I stumbled on two things today that might be goods for folks wanting to delve into the Linux kernel for education or development.
The first is the Interactive Linux Kernel Map. This provides some detail on the layout of the kernel and the interaction between various parts.
The second is the Linux Weather Forecast. This gives you a better insight on the status and progress of features going into the kernel. For example, if the lead developer of the feature is MIA, the feature is probably not going into the kernel in the near term.
Hope this helps your kernel habit!