Private website, need suggestions for good plugins

I've been looking around for plugins to run a website with a private community. I looked around wpmu and I couldn't find any that can do this. Ideally I need to privatise the site using a plugin so non logged in users are redirected to a login page with a captcha and I also need a plugin to send invites to new members. Can anyone suggest a plugin for these things? Most plugins I came across seem to be out of date.