Today (OK, this night) I created some codeswarm movies to visualize the code history of the Hurd.
What's particularly interesting to me in gnumach is the tschwinge - sthibaul effect in march 2008, where development suddenly seems to speed up enormeously.
It clearly shows how much impact just two developers can have - you can have that kind of an impact, too!
The code movies are created from the history of the cvs branches gnumach, hurd-l4 and hurd.
The movies:
in gnumach, red is the "kern", while in "hurd" red is stuff in "release".
.doc. is dark blue and any stuff named .linux. is shown in a blue-green in both. In Hurd-L4 is annotated: It shows libc, gcc, Hurd and L4 kernel commits in different colors.
The hurd wiki movie shows all web commits as "web-hurd@gnu.org", and you can clearly see that most changes are being done via the version control system. There's a way to split the web-commits, but since there aren't many, I leave that for another day 
- article on the ikiwiki page.
Best wishes, Arne