RE: examples of sites with good accessibility

>> For higher ed, I'd like to throw the front door of 
>> www.utexas.edu into the ring as a good model.

>  with fixed width and flyout menus no less.

I do not understand your complaint.  The whole thing scales nicely.  And the flyout menus are fully keyboard accessible.  I actually am quite curious how that is done as they are LI but one does not have to tab through the sub-list items as is the case with typically LI+CSS menus.  Consider the example of another company that pays a lot of attention to accessibility.  Their main menus are relatively tedious to navigate with the tab key:
http://www.adobe.com/

Yes, two-thirds an em is little small, but it quite generally legible for non-body text.  Since it is em, user-control re-sizing is readily provided.

This is a tough audience.