I wrote here recently about Outlook Web Access and its use of WebDAV. Today I discovered another application which uses WebDAV with Exchange: Ximian Connector. This is an extension to Ximian Evolution which enables Linux/Unix-based users to access the full functionality of Exchange rather than the more limited functionality available through the IMAP protocol. From the FAQ page:
Q: What features of Microsoft Exchange are supported?
A: Ximian Connector enables Ximian Evolution to function as a Microsoft Exchange 2000 client by communicating with Microsoft Exchange 2000 servers through the WebDAV protocol. End user data, including email boxes, address books, calendars, and task lists can be stored directly on the Exchange Server, and group data, including free/busy information for group scheduling, is available as well. New features in Ximian Connector 1.2 include public folders, access control and delegation, and direct resource booking.
But you still have to pay Microsoft for each user (on top of the licensing fee for Connector):
Q: Do I need a Microsoft Client Access License (CAL) to use Ximian Evolution on Microsoft Exchange?