Developers of the Customizr theme have created Nimble Builder, a free, powerful yet easy-to-use page builder already active on 50K+ WordPress websites.
It allows you to drag and drop mobile-ready sections on really any page of your site, including home, posts, pages, products, archives, 404, search pages, …
You can insert simple text zones, but also create video backgrounds, insert post grids, column structures, buttons, widget zones, maps, icons, and much more, or use pre-designed sections with professional parallax effect.
The plugin is lightweight and has been designed to integrate seamlessly with Customizr and any WordPress theme.