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openlibrary.org
Search millions of books on Open Library, (available through digital lending). All it takes to get a “library card”? An email address.

untools.co
Benefit from a collection of thinking tools and frameworks. Categories including systems thinking / Decision making / Problem solving / Communications, etc

12ft.io
Want to read an article, but there’s a paywall? Simply insert the URL into 12ft Ladder. All sites have a non-paywall version they send to Google for SEO. 12ft finds the cached, un-paywalled version of the page. Now you’re in.

osintframework.com
OSINT framework focused on gathering information from free tools or resources. The intention is to help people find free OSINT resources. Some of the sites included might require registration or offer more data for $$$, but you should be able to get at least a portion of the available information for no cost.