Google Earth Engine
- "A cloud-based geospatial analysis platform that enables users to visualize and analyze satellite images of our planet"
- Is the software free to use and/or Open Source
- Most/All of it's Datasets are Open Source
- Earth Remote Sensing Satellites (Could one day dive into all the specific missions / satellites / constellations / companies, for now just this page on data sets should be fine)
- Planet Labs