Mashup pages collect multiple sources of information and display them all on one page. Many mashups focus on social media outlets, so that a single page can incorporate a school's Twitter feed, Facebook wall posts, blog posts and so on.
Check out some examples of Social Media Mashup pages on the Finalsite platform by viewing our Pinterest board: https://www.pinterest.com/finalsite/mash-up-pages/
At the most basic level, a Mashup page is a page with a number of elements configured to display content from selected sources. To get a peek under the hood at how a Mashup portal page is constructed, you can find one on the FA Sandbox site. The sandbox's "Mashup" page is a great example of one that is already set up, and you can see how it's put together. (The sandbox site is accessible under the Support dropdown in your admin interface, by clicking "FA Sandbox").
Social media elements in Composer can be used to construct a social media mashup design on a new page.
Finalsite provides custom design services for Social Media Mashup pages for any features that are not available within the editor. If you're interested in working with us to build out your mash-up page, contact the support team or firstname.lastname@example.org, and we can work with you to inspire some ideas.