Get it while it's hot: Jim Kalbach's book "Designing Web Navigation" (O'Reilley) has just been released. In Jim's own words (from his new blog, Experiencing Information):
Since web navigation design touches most other aspects of web site development in some way, the book necessarily paints a broad picture touching on many areas, including things like user research and visual design. But as much as possible the focus throughout remains clearly on creating an effective navigation system. I always try to bring it back home to web navigation whenever the conversation touches other areas.
I can wholeheartedly recommend it (I read some chapters in advance :-)).