KDE Migrant allows you to migrate your existing KDE/Plasma/apps configuration to a new computer. Good when changing computers or cloning one user configuration for other users.
Raspberry Pi (and Linux) simple remote monitoring tool with dashboard for multiple RPi devices. It works for any Linux device.
Bicycle Master Plan is a bike map that allows visualizing cycling related data from different sources in multiple layers. Built heavily around data from OpenStreetMap, it allows full visual customization using CSS.