For the AD logins, go with Likewise Open. Take your time looking through the config files in /etc/likewise, as well as the documentation on the website. Very useful in terms of managing users. Example, I didn't know I could restrict logins to members of a local group.
As far as mounting servers, there are several ways. Since you're using Gnome, I'll leave out smb4k, since it's largely KDE based. The latest versions of Gnome have included the ability to mount network shares via GUI. I believe it uses FUSE to allow the user to do this without root privileges. ONce it's connected, it actually mounts the share on a directory inside the users ~/.gvfs directory. You can create Bookmarks or shortcuts on the desktop, then add these to the system's default /etc/skel, or use something like Sabayon to create the profiles you want.
Only downside to using FUSE is it's a bit slow. If you want more speed, consider using mount.cifs, though this is a command line tool and is less user friendly. You'll have to cook up something via shell or python script and wrap a GUI around it to make it more user friendly. Actually, smb4k above uses mount.cifs. You'll also need to set the sticky bit on the mount.cifs and umount.cifs commands to make them user executable. The upside to mount.cifs is that it's fast and assuming everything else is optimal, you'll get the max throughput you can expect from cifs.