Mac OS X,  Mac OS X Server

Mac OS X Server: AutoFS

AutoFS is greatly improved in Leopard.  To set up an automounting sharepoint in Leopard, use Server Admin from /Applications/Utilities.  

We described how to setup a share point in this article:

Mac OS X Server 10.5: Sharing Files the New Way

Once you have set up your share point then you may want to make it an automounting share, or you may want it to automount and not be visible for users, as in the case of a home directory automount.  To create the automount you would browse to a folder from File Sharing and once shared, place a check mark in the box for Enable Automount.  From here, click on Edit and select a Directory to push the automount from.  Then select your protocol (AFP vs. NFS death match to come) and select the use.  For most cases, the default User home folders will be what you might use.   If you are using home folders then you can click OK and save your settings and enter your Open Directory (or other directory service) administrative password.

To verify it was created properly look at Automounts in Workgroup Manager (WGM).  Here enable All Tabs and Inspector from WGM Preferences.  Then click on the tab with a bullseye (Inspector tab) and choose Automount from the drop-down list.  The newly created automount should appear and you should be able to view any attributes it has.