Lee Ambrosius (Beyond the UI blog) has updated the AutoCAD Command Database that details changes to AutoCAD commands and System Variables since AutoCAD R12. The AutoCAD 2010 Commands are updated and Lee is completing the System Variables. The command map is a simple map where you can see what has been added, changed as well as removed over the past many years in a easy visual chart. If you want a PDF of the command map database, just register for free.
Command Database page - http://www.hyperpics.com/commands/index.asp
Thank you Lee