I know how to have the connection established at login, but I don't know if it's possible that the Finder doesn't open a window of the server root...
I've tried the "Hide" checkbox, but this doesn't help. (I'm on Snow Leopard)
Instead of whatever method you are doing now to mount the server, I would recommend a script which is launched at login for all users.
Your best options are either a LoginHook or a launchd process installed to /Library/LaunchAgents/
You will then need to figure out the syntax for the mounting the drive.
I decided I wanted to check this out further myself, and created this launchd script:
which I placed at /Library/LaunchAgents/luoma.mount.blackbook.plist (owned by root)
The script can be found at http://f.luo.ma/mount_blackbook.sh (note: script will display in browser window, to download, use click-click/save-as)
In OS X Server, you can specify a share as an 'automount'. Is that what you had in mind?
Then, when your users authenticate against your Open Directory server, they not only see their desktop, but are automatically connected to a server sharepoint.
You could mount them with a simple Automator app that's added to the login items. You would just add a "Get Specified Servers" action, add the servers to it, then add a Connect to Servers action. It will mount all the specified servers without opening their windows.
When you add your servers, be sure to include the name of the share point you want to mount, something like
Another option (one which I haven't tried) is to disable Finder opening a new window whenever a new volume is mounted.
I believe the proper syntax is:
Of course this will change the behavior for more than just these particular items.