Jekyll is a static website generator apparently written in Ruby. http://jekyllrb.com/ What this means is you write page content in some format, then with Jekyll generate an HTML website with navigational stuff etc. The HTML website then can be served by Apache at high rates of speed.
Jekyll includes a bunch of tools for importing from a variety of other blogging platforms, including Wordpress, Drupal and Blogger. https://github.com/mojombo/jekyll/wiki/blog-migrations
A nice blog post went over why to leave Drupal, and why to choose Jekyll, and how to do so. http://www.garron.me/linux/switching-drupal-jekyll-migrate.html
The guy's reason? His blog had grown pretty popular and was seeing thousands of page hits a day, and routinely getting top rank in Digg. It meant having to migrate the site from shared hosting to a VPS, and then learn the arcanities of nginx, varnish, etc, all just to host a blog. Specifically: "As you can see in order to keep a server ready to receive the next tsunami of visits, I had to do too much work keeping Apache, PHP, MySQL, Nginx, Varnish and Drupal up to date and secured, also being sure that all of them could work in sync."
That's too much overhead (voice of experience) for a blog.