Static Site Generators (SSG) aren't a new option, but they have been gaining popularity in the past few years. One of the oldest of them all, Jekyll (http://jekyllrb.com/), has been around since 2008 and is used to power GitHub's pages functionality.
CMS software, such as Wordpress or Drupal, build each page when it's requested, gathering data from MySQL or MongoDB, then running it through a template engine. This means, that on each request to the server, the entire page is built from scratch. For the majority of sites this is unnecessary overhead as they only change when new content is added by their author(s). It can also lead to performance and security issues.
An SSG does the exact same thing, but instead of doing it on each request, it's done in advance. When changes are made to the website locally, the SSG leaps into action and renders each page. Whether the site was originally built in Python, Ruby, PHP, or .NET, the SSG delivers plain HTML...