OpenEnergyMonitor.org provides open-source tools and technologies for energy monitoring and working towards sustainable energy goals. The site shares code, documentation, and designs to empower users to build their own energy monitoring systems and collaborate on solutions. Examples include monitoring home electricity usage over 4 years and seeing a 47% reduction, solar PV monitoring, bee hive monitoring to detect swarms, and remote heat pump performance monitoring. All resources are freely available under open source licenses to promote innovation, learning, and sustainable energy problem solving.