1. A raspberry pi 3 on which I use git-annex to archive data on a bunch of large USB disks.

2. A raspberry pi 2 at a different location which provides off-site backups for the data archived by the first pi

3. A raspberry pi zero to run magic mirror on a leftover screen (I cannot be bothered to turn it into an actual smart mirror though)

4. And I recently added another raspberry pi 3 to play with RetroPie