I was looking for the open source membership solutions as well, and tried Drupal, but finally get Joomla because I prefer its architect.Also, finally get this component to work perfectly to manage my own membership website:
Or you can find it here:
It works quite well for me.
I would look into wordpress. I personally use wordpress as a CMS, ecommerce, blog, and community site. I have also built these sites for myself and clients.
Wordpress has many plugins for what you are looking for. With wordpress you can create a membership, ecommerce and blog site all in one. Im sure you can do it with Joomla and Drupal but I haven't used them.
I personally have had much success with wordpress.
PM me if you want the links to the specific plugins.