Part of a website only accessible to users Is it possible to restrict a part of a website to craft user-groups?

For instance if I want show an internal Blog to members-only.

And is it possible to moderate user registrations? So when somebody registers an Admin has to approve it first?
It is! You can use the requirePermission tag:

{% requirePermission "yourPermission" %}


See the full documentation here. Keep in mind this list as built in permissions but you can also add custom permissions through a plugin should you require it.

As far the second question, I'm not 100% sure but I believe you can set "enabled" to "false" when creating a registration form. See further details here.

Update: You can also use isInGroup