I posted to twitter.com

Advice to @velvetsarah about choosing a blog/cms with private members

http://twitter.com/davidm_en/statuses/970387127

If it's a pure blog the obvious choice is WordPress which has an advanced plugin to allow self registration and WP supports private pages... But there are several options wether it's blogs or CMS. In the CMS department there is Typolight, less nerdy than Drupal, more flexible than Joomla.