Wren - Offset your carbon footprint by saving rainforests
Clock.saver - A simple clock screensaver based on Braun watches ⌚
Klima - Go carbon neutral
Capture - A great free screen capture utility that allows you to capture either a window or the desktop and save it to either a file or the clipboard.
Website Carbon Calculator - Find out the how much CO2 your website emits
Joro - The Fitbit of carbon emissions