> Can anyone recommend any good books/articles/online resources, etc, 
> related to BSD kernel internals. I have a set of excellent books by 
> Richard Stevens on Unix system and network programming, which I use 
> extensively, however I would like to fully understand the lower 
> semantics of Unix, i.e. BSD kernel design/implementation.

I personally like these two books:

* The Design of the Unix Operating System, Maurice J. Bach
* The Design and Implementation of the 4.4 BSD Operating System,  
  Marshall Kirk McKusick, et al.

The following book is useful for getting a more detailed overview of 
filesystem design:

* Unix Filesystems: Evolution, Design and Implementation, Steve Pate

But be aware, that the the "Design of..." books listed above are a bit 
old but they are good for understanding the design of Unix and BSD kernels.

The Tanenbaum book is very nice, but a different beast altogether
(both Minix and the book). It is good for learning Unix-like operating
system basics, but not for diving into *BSD code.

-- Daniel