American Mathematical Society (AMS)
Computational Mathematics and Statistics Section of the Oak Ridge National Lab
Department of Mathematics of the Russian Academy of Sciences
Institute for Mathematics and its Applications (IMA)
Mathematical Association of America
Coverage: current MathWorld is a comprehensive and interactive mathematics encyclopedia intended for students, educators, math enthusiasts, and researchers. Published as the CRC Encyclopedia of Mathematics (3rd ed. 2009).
Online library of resources for science, technology, engineering, and mathematics education and research.
The Engineering Pathway is a portal to high-quality teaching and learning resources in engineering, applied science and math, computer science/information technology, and engineering technology and is designed for use by K-12 and university educators and students. Resources include support for ABET accreditation, research and scholarship, curricula development and extracurricular activities for students.
This web site is from BUBL Link. "BUBL LINK" is the name of a catalogue of selected Internet resources covering all academic subject areas and catalogued according to DDC (Dewey Decimal Classification). The website's content covers comprehensive mathematical topics at a variety of sources.
Coverage: current The NIST Handbook of Mathematical Functions, together with its Web counterpart, the NIST Digital Library of Mathematical Functions (DLMF), is the culmination of a project that was conceived in 1996 at the National Institute of Standards and Technology(NIST). The project had two equally important goals: to develop an authoritative replacement for the highly successful Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, published in 1964 by the National Bureau of Standards (M. Abramowitz and I. A. Stegun, editors); and to disseminate essentially the same information from a public Web site operated by NIST.
This website contains lots of free internet reference resources recommended by American Mathematical Society. Under Reference Section, there are free online dictionaries and handbooks on a variety of topics.
Yahoo Mathematics. Very popular site on the Yahoo Directory which is a good jumping off point. Sites are evaluated and you can restrict your search to just mathematics categories instead of the entire Web.
Mathematics Gateway - index to math Internet resources. Targets researchers and students in in higher education. An award-winning service, also offers full-text journals.
Math Forum - best general math site on the Web. Gold mine for undergraduate students, as well as quality online mathematics education for professors.