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The Khan Academy, which began in 2006, is a free website that currently contains more than 1600 short (10-20 minute) videos that teach a variety of subjects, especially in math and science. Louisiana-born creator Salman Khan, a former Silicon Valley investment manager with an MBA from Harvard, hopes that Khan Academy will bring a “free, world-class education” to the world. Mr. Khan narrates all the videos using only a blackboard and colorful writing.
arXiv is a free distribution service and an open-access archive for 1,758,918 scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics. Materials on this site are not peer-reviewed by arXiv.
MathSciNet® is the authoritative gateway to the scholarly literature of mathematics. MathSciNet contains information on over 3 million articles and books, with direct links to over 2 million articles in over 1,800 journals. MathSciNet includes expert reviews, personalizable author profiles, and citation information on articles, books, journals, and authors.
Open Math Notes is a repository of freely downloadable mathematical works in progress hosted by the American Mathematical Society as a service to researchers, teachers and students. These draft works include course notes, textbooks, and research expositions in progress.