System

Redshift Control Plasma – free and open source applet for automatically adjusting color temperature of screen depending on time of day in KDE Plasma

f.lux – free and open source program that adjusts the color temperature of the monitor in accordance with the geographical location and time of day set by the user

KRuler – free and open source on-screen ruler for measuring pixels for Linux

eViacam is a free and open source mouse replacement program that moves the cursor when the head moves

Caffeine – free and open source utility for disabling the screensaver in Linux

Meteo is a free and open source weather forecast program for the coming hours and days with data and maps