DavMail is a POP/IMAP/SMTP/Caldav/Carddav/LDAP exchange gateway allowing users to use any email/calendar client (e.g. Thunderbird with Lightning or Apple iCal) with an Exchange server, even from the Internet or behind a firewall through Outlook Web Access. DavMail now includes an LDAP gateway to Exchange global address book and user personal contacts to allow recipient address completion in the mail compose window, and full calendar support with attendees free/busy display.
SabreDAV allows you to easily integrate your existing Web application with WebDAV. It supports most of the common clients, including the Mac OS X Finder, the Windows XP/Vista Explorer, DavFS2, Cadaver, NetDrive, and WebDrive. It supports class 1, 2, and 3 WebDAV servers. It implements RFC2518 and revisions from RFC4918. It also implements RFC2617 (Basic/Digest auth).
jGoogleCalSync is a Java application that uses the ICS file format to access and upload calendar information in GMail's Calendar. The application has been built to upload Lotus Notes calendar information. Once the Lotus Notes information is in GMail calendar, it can be synchronized via CalDAV towards an iPhone or other calDAV-enabled devices.