A quintessential free stack, if you are using an ExtraContent-enabled RapidWeaver theme in conjunction with the Stacks plugin.

ExtraContent was invented in 2008, by a group of likeminded theme developers, who wanted to give their theme customers more control over the placement of content in evermore sophisticated theme designs.

In summary, ExtraContent lets you break-away from a traditional two column content / sidebar theme layout and effortlessly embedded content into additional containers elsewhere on the page. Containers such as social networking bars, banners, hero units, footers, and much more besides.

To this day, ExtraContent remains a collaborative effort between different developers. ExtraContent is supported in hundreds of RapidWeaver themes and frameworks.