<p>I had svnserve configured to look at directory "Foo" for the repository it served. Now I changed the configuration from one repository to multiple repositories, all contained in one directory "Bar". I reconfigured svnserve to look at "Bar", but now my client can't find any repositories. What am I doing wrong? Do I need one service for each repository?</p>

<p>Thanks, Miel.</p>

Did you configure your client to use svn://svn-server/Foo ? (Assuming Foo and Foo2 are repositories in directory Bar, which you're serving)
Since you're serving "Bar" now ("svnserve -r /repositories/Bar" instead of "svnserve -r /repositories/Bar/Foo") you should make a change on your client-side repository URL.
Another solution would be to fire up multiple SVN servers with different ports using the --listen-port parameter. That would also change your URL.
Yet another alternative is just adding new projects to your single existing repository; note that you'll have a single repository configuration this way -- and that means a single set of users, simpler access control, etc.