Access MVPs Gunter Avenius and Peter Doering have setup a site with information on ribbons from Access point of view, with lots of VBA and XML samples. The site is online in English on

http://www.accessribbon.com

and German 

http://www.accessribbon.de

You might also take a look at my blog post a couple weeks ago. (I was surprised more of you didn't click on it.) It has a sample database and a few screen shots with ideas about how to design interfaces that take advantage of the strengths of the ribbon.

http://blogs.msdn.com/clintcovington/archive/2006/12/08/msdn-article-on-creating-custom-ribbons-in-access-2007.aspx