In an earlier post, I mentioned two uses I saw for "Reusable Content" in SharePoint 2010, but that I needed to research these further. After doing this research, and given the particular client's need, I elected to use Page Layouts instead. This allowed me to put common display elements used for home pages of subsites in one place.
In order to make Page Layouts work, we had to enable the SharePoint Server Publishing site feature on each site. Next, we had to create a new Home.aspx inside "Pages," and make this the site's home page. "Pages" is the library for SharePoint "Publishing Pages," and one of the benefits this type of page gives you is the ability to create and use "Page Layouts."
Standard "Site Pages," on the other hand, use "Text Layouts," which are different. Confused? You're not alone. The documentation for all of this is difficult to track down. But if you want reusable, manageable page layouts, "Publishing Pages" is the way to go.