Mac OS X Server supports WebDAV and allows iPhones/iPads to connect, store and retrieve files.
While Mac OS X can access WebDAV servers from the Finder using "Connect to Server" (Command+K) attempting to connect to the root of a Mac OS X server or any other assumed location results in an error:
There was a problem connecting to the server “theserver.domain.com”.
Check the server name or IP address, and then try again. If you continue to have problems, contact your system administrator
I can only guess that there is some special URL/URI that is necessary but what?