I just relaunched our company's web site http://www.zirona.com, now entirely powered by WP. Aside from implementing a nice design, I put a lot of effort into accessibility.
For the German speaking among us, there is a catalogue, sort of a check list for the BITV (which is the German version of "section 508") at http://www.bitv-test.de. As our company has already been successfully reviewed by the BIK project with our old site, I have done everything to conform with the bitv-test.de catalogue again. This includes very fiddly requirements, (e.g. there must never be a link to the page currently displayed, which is tough to implement on a CMS).
However, I think I managed conform with all the requirements. In order to achieve this, I have adapted some plugins, especially the Fold Page list and Fold Category list (which are already great plugins by default). At the moment, the modified plugins are not available for download, nor have I talked back to the respective developers. But if anybody wants to have them, or wants to know about techniques used, I'll be glad to help.
However, I'd be glad to hear some feedback on the new site's design as well as the accessibility. Of course, bug reports are welcome, too.