Administrative Assistant Handbook: What should be included?

I am working on the same project. Each of the Administrative Aides at my company work in a different program but some of thier duties are the same and other different. The duties that are the same should go toward the front of the handbook. I have included a Welcome page, instructions on how to handle the phone lines, a list of departments, department heads and staff including their phone numbers. We are working on the duties that are different and listing general information for cross training purpose but detailed. This is an awesome project and I am happy to hear that I am not the only one having such a project.
If you have items you are including that I did not mention, please let me know.