MSDN article "Ribbon Extensibility in Access 2007"
A couple of months ago I spent a few days learning how to write XML for ribbons. I got pretty excited about the types of new interfaces that users can create without any code. I think you will find it is easier than you might think. This paper is the end product of a blog post I was going to write. It turned out to be so interesting that we decided to push it through the meat grinder and provide a uber doc that covers the basics of ribbon creation. Viki did a ton of work gathing all the extra details--thanks for the help. Here is the summary, URL, and picture of a couple screen shots:
Learn how you can create a custom Ribbon for an Access 2007 database by using only Ribbon extensibility markup XML and macros. Discover how to create a command space without writing any code and also learn about more advanced scenarios that require code. (28 printed pages)
Custom Form Ribbon:
Custom Report Ribbon:
Here is a link to the sample database http://www.microsoft.com/downloads/details.aspx?familyid=291704cb-655a-491f-8089-566be7d2e9b0&displaylang=en.
If you are looking for an examples of more advanced customization here is a blog post by Erik months ago http://blogs.msdn.com/access/archive/2006/07/13/664757.aspx. This sample has more examples of dynamic galleries, labels, etc.