Automaticaly update Active Directory based on an intranet webpage (500pts)

First off let me say that this is not a problem that we are experiencing but a project that we would like to implement. First off a little background is necessary.

Aside from running Win2k3/AD we have a program that pulls information from Active Directory in order to create our email signatures automatically. For those interested the product is Policy Patrol from RedEarth Software.

What we would like to do is have some sort of webpage on our intranet site that would allow the users to view and modify some of their information that is stored in AD. We would lock down certain fields so that they couldnt change their title, manager, etc. This would mainly be for updating their contact information, firstname, lastname, telephone numbers, addresses, etc.

Obviously this would require some type of authentication to ensure that the users dont change other peoples information, that is not really what I am interested. I am interested to know if anyone out there has done somthing along these lines and how you do it. Was it a completely custom build or is there some third party tool.

Basically I am looking for ideas, suggestions, reccomendations, warnings on this project.

Thanks