I've written up some notes on how some of the low-level network stuff in FreeBSD works. It's a work in progress and so probably has lots of errors.
FreeBSD networking notes.
Other Random Projects
Of late I've been working a bit on
Jon Harrop'sSmoke Vector Graphics project.
Jon's written some excellent code which offloads most of the vector graphics rendering onto graphics hardware, via OpenGL. The results are pretty amazing: complicated images rendering, panning and zooming at 60fps on very modest hardware. My efforts so far have been focussed on providing SVG import. If you're curious about SVG then a good place to start is
Raph Levien's
interim report on the Gill project -- quite a sobering read!