I have created a series of articles regarding the development of an embedded NetBSD system. I start with the basics of building a kernel and developing a true minimum filesystem. These first steps have very little functionality, but embedded software design typically involves stripping out everything and then adding just the functionality needed. The goal of these excercises is to develop a methodology that creates a simple system. After you know the process, adding additional functionality to the system is straightforward. Here's a list of topics I would like to cover as well.
Embedded System Basics
A tour of the rc.d initialization system.
Using the syslog facility for messages and error reporting.
Remote debugging of the kernel and userspace programs.
Processing a core dump.