...
Dav server is built into Sakai, right out of the box. Point your dav client at http(s)://<your server dns name and port>/dav/group/<some site id> to see that site's resources. Or to see a person's resources from a my workspace, use /dav/user/<user id>.
WebDAV issues (particularly with native XP client)
UCT has set up a page to track a number of issues.
https://www.connect.uct.ac.za/sakaiwiki/index.php/WebDAV_Notes