As Bastian has pointed out, wiki.debian.org has a butt-ugly theme. I agree.
Some of the people that were present in Extremadura in September know that I was working at the time to make a wiki theme more integrated with the www.debian.org theme.
The result is partially complete, but is better, IMHO, than the ugly default theme. Sceenshots and the source is available (in a darcs repo). If anyone cares to continue and close all the remaining points, I would be glad to see that theme changed.
Unless somebody does something about both issues.
Comments are welcome! Contributions are welcome, you just do:
darcs get http://users.alioth.debian.org/~eddyp-guest/darcs/wiki.debian.org_theme/
And hack on that modern-wiki.debian.org theme