The marketing team has produced three great tools for helping you find commands in the ribbon for Word, Excel, and PowerPoint. Click on the Start the Guide link to launch the interactive tools. These tools visually show you how to find commands from the previous version to the new ribbon. Here are the links:
Mor (the Access marketing guy) is working on a version for Access but it is a bit more complicated because of all the different mode switches and ribbons. I will let you know when it is available.
Comment from Alan: In the meantime, there is an Excel file you can download from http://office.microsoft.com/en-us/access/HA101666061033.aspx (at the bottom of the page) which tells you where Access 2003 menu options have relocated to).
Edited 3/13/2007 with comment from Alan.