I have updated the System Variables list on my website to now list all of the new or changed system variables in AutoCAD 2009. Like the Commands list, it is really amazing to see all the system variables back to AutoCAD R12 with those that are still in AutoCAD 2009 today and the ones that have been added since then. Enjoy the list, there is still some work to do yet but for the most part it is complete. The work that is outstanding is the description and available values of the system variables, all descriptions should be updated in the upcoming weeks.
System Variables List - http://www.hyperpics.com/system_variables
For more about past versions of AutoCAD, check out Shaan Hurley's Unofficial AutoCAD History Page.
As for the PDF files that are related to each of the Command and System Variables lists, I will start work on those very soon and will post once those have been updated. If you have any questions or comments, let me know.