Government of Canada Common Look and Feel
The Government of Canada's Common Look and Feel (CLF) standard governs branding, usability & accessibility standards for government departments on the internet.
http://www.tbs-sct.gc.ca/clf2-nsi2/
http://en.wikipedia.org/wiki/Common_Look_and_Feel
Several Open Source projects have implementations:
http://tbs-sct.ircan.gc.ca/projects/gcwwwvar?jump=files&lang=eng
Here is a proof-of-concept theme to demonstrate that a CLF theme could be made for Tiki:
http://gcca.ourwiki.net/