<p>Just need to use find a simple way to have AD authenticate as the login for a Sharepoint site. This fairly quick and simple to get going ? </p>

<p>Thanks! </p>

For SharePoint 2007, see this
article
.  You probably want to set it up to do Windows integrated authentication with NTLM.  Getting authentication working is probably not too hard, getting your site setup the way you want with permissions/authorization working probably isn't.  Depends on how complex your site is.  I wasn't directly involved but I know that it took a few months to get our intranet up and bug free.
One recommendation that I would have is to use AD groups or SharePoint groups that contain AD groups rather than individuals to control access.  It's much easier to clean up AD group membership when an individual leaves than to track down all the places where you've given them individual access (including membership in SharePoint groups).