Make it a torrent machine with a torrent client that supports a "black hole" function meaning it'll scan a certain folder for torrent files and automatically download those detected.
Download automation.
CouchPotato downloads movies automatically, easily and in the best quality as soon as they are available.
SickBeard Automatically finds new and old episodes for you and it works with your current download client!
SickRage Automatic Video Library Manager for TV Shows. It watches for new episodes of your favorite shows, and when they are posted it does its magic.
Sonarr is a PVR for Usenet and BitTorrent users.
FlexGet is a multipurpose automation tool for content like torrents, nzbs, podcasts, comics, series, movies, etc.
sabnzbd makes Usenet as simple and streamlined as possible by automating everything we can.
nzbget is a binary downloader, which downloads files from Usenet based on information given in nzb-files.
headphones is an automated music downloader for NZB and Torrent, written in Python. It supports SABnzbd, NZBget, Transmission, µTorrent and Blackhole.
Host a VPN with OpenVPN.
Host your own git with Gogs, this is possibly extremely useful for you.
Transform it into a router with pfSense.
Host your own cloud with something like owncloud.
LAMP, you know what it is.
Most of these suggestions come straight from the resource collection on the homelab subreddit. This list is also worth spitting through.