Public REST API to track JWST's current status
API data source: https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.html
Public endpoint: https://api.jwst-hub.com
Software that emulates the guidance computer of the Apollo space capsules.
Free datasets made available by Amazon. Stuff like an atlas of the Galactic Plane, NASA NEX data, the Human Microbiome Project, the Enron emails, Freebase, and the Marvel Universe's socialgraph. The Google Books Ngrams corpus is in here, also, alongside the Westbury Lab USENET corpus.