In the book Mac OS X Directory Services v10.6, we walk you through extending augmented user records with home folder as an example. http://www.peachpit.com/store/product.aspx?isbn=0321635329

But – it is one thing to make an attribute available and populate it with information, and it is another task to get the OS or an application to care.

Are you referring to the Web Proxy, which you can set with the advanced pane of the Network system preferences, on a per-interface basis ? I don’t know if any browser other than Safai pays attention to the setting…

When you use Workgroup Manager’s managed preferences to assign a Web proxy, it updates the dsAttrTypeStandard:MCXSettings attribute; in my experience, managed preferences is not a good candidate for augmented user record extension, even though that’s was one of the first things that many people wanted to use it for when augmented user records first appeared.