WeeWX - Open source software for your weather station
weewx is a free, open source, software program, written in Python, which interacts with your weather station to produce graphs, reports, and HTML pages. It can optionally publish to weather sites or web servers. It uses modern software concepts, making it simple, robust, and easy to extend. It includes extensive documentation.
OSMC - Open Source Media Center
OSMC (Open Source Media Center) is a free and open source media player based on Linux. Founded in 2014, OSMC lets you play back media from your local network, attached storage and the Internet. OSMC is the leading media center in terms of feature set and community and is based on the Kodi project.
Home Assistant - Open-source home automation platform
Home Assistant is an open-source home automation platform running on Python 3. Track and control all devices at home and automate control. Perfect to run on a Raspberry Pi. Track the state of all the devices in your home, control all your devices from a single mobile-friendly interface, and set up advanced rules to control devices and bring your home alive.