This isn't even the most exciting or useful part! They also offer an app called FreePrints Photobooks. This one offers a free 5x7 standard softcover photo book each month, again only pay shipping. "No subscriptions. No commitments." I especially like that part.
It's up to you when it comes to how creative you want to get with these. I imagine focusing on one ancestor and printing a book of photos of them, documents, maybe a graphic that is a map of their ancestral home, headstone photos, and so on. Shipping usually comes out to be between $5-$10, which isn't bad for a gift with meaning! And a great way to share all your hard research work with the family any time of the year.