Update:: There is no guarantee that this plugin works with the current version of WordPress. I have not been keeping it brushed up and ready as things have been changing with WordPress. If I do fix it in the future, I will notify you of the the fact here first.
I finally got to rewriting the Registered Only plugin. The new version works on WordPress version 1.5.1 and 1.5. The older version had some issues. The new version is much lighter, and uses a core WordPress function, and so should work without any issues. If there are any issues, please report them at the wp-plugins.org issue tracker.
The registered only plugin restricts access to the WordPress weblog and site (including Pages, if any), to registered users who are logged in. This will be useful for those that want a private blog, or a blog restricted to friends and family. Consider it the WordPress version of a friends-only Livejournal or similar.
The latest version has the tag (version number) 2005-05-12-2000. I will be using a YYYY-MM-DD-HHMM (in UTC time) (based on the ISO8601) format for version numbers, since it seems easily sortable, and conveys information about the freshness of the version. You can download it from the wp plugin repository, save the file as registered-only.php and then upload it to your wp-content directory on the web server.
There is now a readme file with relevant details.
Many thanks to the many users who wrote in regarding this plugin over the days. Leave me a comment if you use the plugin and like, or better still, dislike it.