A Content Management System (CMS) by w³ – Web Design & Online Marketing that's really simple. It is very easy to use, even for someone with little experience in computers. It also doesn't need time-consuming and cumbersome installations, it's "in the cloud".
It comes with a ton of great features, including support for page templates, full source editing, per-page permissions, change notifications, user activity monitoring, a Google Analytics dashboard, and much more.