FYI, I gave an hour and a half Hurd lecture yesterday at Catholic University in Washington, D.C.
I put a screencast of the lecture on youtube:
The first part of the video is a general discussion of high performance computing, leading into my own work developing Hurd as a cluster operating system.
The Mach/Hurd specific part starts at 43 minutes.
I developed some tikz macros to illustrate Mach/Hurd concepts using LaTeX. For example, there's an illustration of Mach IPC at 51:20, the memory object protocol at 1:09:30, and the netmsg server is illustrated at 1:16:25.
Others might find these macros useful for constructing similar presentations. If so, I've got the LaTeX source for the slides in my github hurd repository here:
I might revise it a bit; the macros are a bit clunky.
A finished PDF is available here:
Could we add that to the collection of presentations that we've got on the documentation page?