User objects have an employeeID attribute but it doesn't appear by default in active directory users & computers.
Sakari Kouti has written a great script to help with this. You can find that script here(employeeID.vbs)
Download the script and save it on your PC. I've put the script on my C drive in a folder called AddID
In ADSI Edit go to the configuration container and navigate to CN=DisplaySpecifiers, CN=409)
In the right pane find CN=user-display and right click and select properties.
Select the adminContextMenu attribute. Add the following value
2, Employee &ID, path to script
Note: If 2 is in use just pick the next number. In my example I've put the script in c:\addid\employeeid.vbs
UPDATE: I should have added this when I first posted this but thanks to Rob Sampson for pointing it out. Rob is one of the strongest scripters I've met and is a valuable member of the IT community.
From Rob (Thanks Rob!):
you could place "employeeid.vbs" in your NetLogon share of a Domain Controller (which then replicates to all other DCs), and have 2. Employee &ID, \\domain.com\sysvol\domain.com\scripts\employeeid.vbs
Screen shot below shows that example in my mktest.com domain.
Now if you use Active Directory Users & Computers you can right click on a user and employee ID should appear.
You can select the field and edit it:
Thanks to Sakari Kouti for the script. He also has a new book coming out called Active Directory 2008 Unleashed
If that book is anything like his last book (Inside AD 2nd Edition) then it is a must have...I've already pre-orderd the new book :)