- Outdoor irrigation control via OpenSprinkler Pi: https://opensprinkler.com/product/opensprinkler-pi/

- Z-Wave home automation via ZWay: https://z-wave.me/products/razberry/

- 2 Custom HAVC thermostats using: https://github.com/jeffmcfadden/PiThermostat

- An NTP server with GPS attached for a time source.

- 2 for weather monitoring (one directly attached to sensors, one that aggregates the data from a few sources and provides reporting)

- A sort of centralized "workhorse" Pi that runs a lot of random cron jobs, etc.

- An Alexa gateway for home automation

- An NES emulator

- An infrared-remote source for turning on/off surround receiver, TV, etc.

- Monitoring of HVAC temperatures/performance

- An intranet server

Assuming I didn't forget anything.