The first question you have after assembling your Raspi is easily, "What can we run?" There's no shortage of projects. In my case, I had one in mind before purchase time. It was Brent Rubell’s Pi-hole Ad Detection on Adafruit.
The idea behind the Pi-hole is to prevent ads from loading. Jacob Salmela also has a walk through of the entire process. It's a good description of how a web page actually loads content, and dispels any lingering mystery about browsing.
In following the tutorial, I saw that Dnsmasq is a key component. This was cool to learn because I remember configuring Dnsmasq from the Archlinux docs under the section for filtering domains. Further scanning of the guides led to details of an Unbound combination for recursive DNS. This configuration stayed on my mind as I played with different recipes, and cemented later as the most minimal for my purposes. To clarify, my idea of the sinkhole is a configuration free of a web server, DHCP, stats or logging.
Again, the objective is to prevent ads. The other benefits cited stem from the elimination of ads: