Franklin Pezzuti Dyer
This is a list of websites, webpages, reference materials, books, tools, and other resources that I enjoy using. Most of them are fun, and a few are actually useful.
List of math resources:
Mathematics Stack Exchange
A Q&A-style community of mathematicians of all levels. Lots of interesting problems and helpful solutions can be found here.
A translation of Diophantus' 'Arithmetica' from Greek. This is an extensive collection of fun, low-commitment, back-of-the-envelope puzzles in the form of diophantine equations.
A (rather dated but still great) book covering various topics in algebra, such as arithmetic, polynomial identities, continued fractions, and many more.
Problems from previous years' Putnam competition exams.
Geometry in Color
Explorations of tesselations, tilings, and geometric transformations, accompanied by mesmerizingly beautiful pieces of geometric art.
List of compsci resources:
New developments in technology, science, mathematics, business, and politics, intellectually stimulating articles, and fun web-apps.
Krebs on Security
A blog covering high-profile security breaches, software and hardware bugs and vulnerabilities, phishing tactics, and other cybersecurity-related issues.
Test your hacking skills on this vulnerability-ridden website that was designed to be hacked.
Laws, theories, principles, and patterns that developers will find helpful.
A universal document converter.
List of other resources:
Index of Bongard Problems
A huge collection of Bongard Problems by a variety of authors, compiled and hosted by Harry Foundalis.
Worldbuilding Stack Exchange
A crazy community where writers, RPG players, scientists, mathematicians, philosophers, and other enthusiasts work out the details of hypothetical worlds.
The blog of Gwern Branwen, full of interesting articles about psychology, technology, statistics, and self-experimentation.
A non-profit library of millions of free books, movies, software, music, websites, and more.