In case your interested:
Center for Digital Government
2004 Best of the Web and Digital Government Achievement Awards
King County's in 4th place this year.
Some common themes among all of these sites. Audience based navigation, personalization, search, and online services.
I've noticed a few government sites that have either purchased or developed their own detailed taxonomy.
Fairfax County uses the Taxonomy of Human Services developed by the Referral Federation of LA County. The state of Connecticut has what seems to be a home grown Taxonomy, though the lack of breadcrumbs makes it hard to tell where you are within the taxonomy. Their are some drawbacks (like occasional awkward navigation) but you can really tell the difference in overall usability.
The other noticeable trend that these two sites suggest an audience centered navigation at the top. Both have some general audience categories on the top page like: "working & living," "doing business," and "visiting." Then separately they list off the offices like the Council, Executive, etc.
I wonder how this works for organizations that serve multiple audiences. I also wonder how much control the actual agencies have in their own placement within the taxonomy.