Pocket-sized cloud with a Raspberry Pi
In my homelab I've got RPis running Minio (S3-compatible block storage), step-ca (local certificate authority), CoreDNS (local DNS), a local gpsd/chrony setup (for local GPS-backed NTP, using the Uputronics GPS hat), shairport-sync (AirPlay server), and some web services fronted by Caddy. A great way to learn and try out various services, Linux distros, infrastructure management options, etc.