Nothing fancy, a Mac Mini with a UPS in the furnace room where my router/WiFi base station is located, with several drives and a MagicJack plugged into it. One 3TB for home stuff like Time Machine backups and my VOD archive and a couple other 4TB drives JBOD'd for nightly remote off-site backups of my company's primary server. Also have a 60-foot amplified USB cable running from that basement furnace room into my baby's room for a cheap home-brew baby cam monitor. Another camera in the garage so I can quickly see if we forgot to close the garage door.
MagicJack, ewww, right? Well, maybe, but hey, it's dirt cheap and works well for my 9-year-old to have a phone at home if he's home alone which we allow from time to time, like if we need a quick grocery store run, etc.
I ran ethernet throughout my house as needed as well, although there are a couple spots I wasn't able to access. Yeah, WiFi is nice but I live in a pretty new neighborhood, lots of younger families like mine, and very crowded WiFi space including the 5ghz band. Since my TV is entirely streaming (Roku and AppleTV) I wanted it to work solidly, reliably, and not be subject to interference from neighbors. I can sit in my living room and see probably a dozen and a half networks pop up. And I've got a couple BluRay players that don't have WiFi, just ethernet. I just ran a single cat5 wire behind the TV, put a little 4-port switch back there and call it good. I've got an older Proliphix network-enabled thermostat too from before WiFi was even very common, which required Cat5 and PoE to function, so I had to run Cat5 to it which was tricky but doable. It's no Nest but I already own it and I can still adjust the temp from my phone when we aren't home.