If you're serving a collection of repositories from a single URL via the SVNParentPath directive, then it's also possible to have Apache display all available repositories to a web browser. Just activate the SVNListParentPath directive:

<Location /svn>
  DAV svn
  SVNParentPath /var/svn
  SVNListParentPath on
  …
</Location>

If a user now points her web browser to the URL http://host.example.com/svn/, she'll see list of all Subversion repositories sitting in /var/svn. Obviously, this can be a security problem, so this feature is turned off by default.