Through your site settings menus, enable the following two Features:
- Office SharePoint Server Enterprise Site Collection features – this is enabled in the Site Collection Features link located in the Site Collection Administration section. Enabling this feature is what put the RSS Viewer web part in my publishing site’s web part gallery.
- Office SharePoint Server Enterprise Site features – this is enabled in the Site features link located in the Site Administration section. You do not need to enable this feature to add the web part to the top-level publishing site, but I think it is a good idea to enable both of these features in tandem.
This puts the RSS Viewer web part into my Gallery and can then be utilised to read content from external sources.