A+ Click is an interactive collection of more than 3700 math problems and answers for K-1 K-12 school program. It defines the personal level of math knowledge. You move up into the next level if you give 5 correct answers in a row. Practice makes perfect.

The American Mathematical Society's (AMS) Books Online makes available full text of over 30 scholarly monographs published by the AMS, covering a range of subjects including algebra and algebraic geometry, analysis, applications, differential equations, geometry and topology, logic and foundations, mathematical physics, number theory, probability, and general interest. Their gateway page organizes titles by subject and author.

Animated features and activities providing mathematics instruction and homework help for younger students (K-3). Each animation is accompanied by quizzes, games, vocabulary, and other activities. Topics include addition and subtraction, multiplication and division, how to use a calendar, how to count and use money, fractions, how to make measurements, and many others. Movies, animations, and activities available via paid subscription; 5-day free trial is offered. Site offers free lesson-plan ideas.

This collection of interactive features and animated movies introduces students (grades 3-12) to mathematical calculations and computations. Categories include algebra, data analysis, geometry and measurement, probability, numbers and operations, and ratio, proportion, and percent.

This site provides lectures, animations, graphics, tests for teaching precalculus, calculus, trigonometry and differential equations.

Course Communities in Undergraduate Mathematics is a collection of online resources for undergraduate mathematics courses. The courses done so far are one-variable calculus, multivariable calculus, and ordinary differential equations. These resources were assembled and cataloged by separate working groups for each course. In addition there is a pseudo-course, developmental mathematics, obtained from Tom Carey's project of the same name. A working group is currently identifying and cataloging resources for a course in probability.

An online derivative calculator that computes symbolic derivatives of mathematical expressions. User input and results are typeset as graphical formulas.

This is a free textbook which covers material for an introductory course on differential equations with some partial differential equations material, though it assumes knowledge of matrix theory. It includes a section on computing Fourier series of polynomials. It also includes a link to the freely available student solutions manual.

This site provides information on solutions to various classes of mathematical equations. There are exact solutions and methods for solving ordinary differential equations, partial differential equations, integral equations, and other classes of functions and transforms. The Equation Archive allows authors to post equations and exact solutions, first integrals, and transformations. There is also an index of named algebraic, ordinary differential, partial differential, integral, and functional equations. Other materials include links to online forums, information on mathematical software, and links to educational materials, publications, and related websites.

Freebookcentre.net's mathematics section contains links to many technical books offered free online, either as html pages or downloadable pdfs. Books are arranged by subject: algebra, geometry, calculus, differential equations, discrete mathematics, linear algebra, number theory, differential algebra, probability theory, trigonometry, and others.

An online integral calculator supporting definite integrals, indefinite integrals (antiderivatives) and improper integrals. User input and results are typeset as graphical formulas.

Investigations is a complete K-5 mathematics curriculum, developed at TERC in Cambridge, Mass. It is designed to help all children understand the fundamental ideas of number and operations, geometry, data, measurement, and early algebra. The curriculum has four major goals: to offer students meaningful mathematical problems; emphasize depth in mathematical thinking; communicate mathematics content and pedagogy to teachers; and expand the pool of mathematically literate students. This site includes descriptions of the units in each grade, K through 5; ordering information; and information on professional-development workshops designed to facilitate introduction of this curriculum.

This site offers 18 curricular modules based on primary historical sources for undergraduate courses in discrete mathematics, combinatorics, logic, abstract algebra, graph theory, analysis of algorithms, data structures, automata and formal languages in computer science. Designed to capture the spark of discovery and motivate the subsequent lines of inquiry, our projects are centered around key historical sources that led to the development of selected topics in the above fields.

This collection of open-source, sharable math applets includes interactive components accompanied by at least two curriculum units. The interactive components are written in Java, Macromedia Director (Shockwave), or Macromedia Flash, and the curriculum units are editable, for instructors who wish to make their own modifications. The collection is searchable by category (application type, spreadsheet-based, and others), subject (arithmetic, set theory, algebra, and others), and by keyword. Participants are also invited to submit their own osslets, which are reviewed for inclusion in the collection by an editorial board. Requirements for submission are included.

This Wiki-based image gallery features imagery related to mathematics, with explanations of the math principles behind the images. Each image is accompanied by information on its creator, source, field of mathematics, a brief explanation of the principles behind the image, and links to additional information (where available). The gallery is searchable by keyword and browseable by title, author, field of mathematics, and grade level. Users are invited to contribute images and explanatory material to the gallery.

Math Tricks is a site dedicated to collecting games and articles to spark the interest of math non-enthusiasts.

Mr. Martini's Classroom is designed to give elementary-school students the opportunity to practice and reinforce math skills online. The whole spectrum of K-8 math topics is covered - multiplication, division, fractions, decimals, geometry, pre-algebra, and kids math facts. Online tools include math flash cards and self-correcting quick quizzes. There are also printable math worksheets.

Mr. R.'s World of Math is a teacher-created collection of math videos, poems, stories, songs, and challenges to help students master basic math functions. In addition to videos there are printable student handouts for the math challenges and several powerpoint demonstrations.

This page features weekly mathematics problem sets that are designed to teach intermediate and upper-level students about space weather. The downloadable problem sets include one or more math problems to be solved using the information provided, a teachers' guide or answer key, and an inquiry question about the results. The web page features the current week's problem set, sets from previous weeks, and an archive of problem sets from past years. There are also downloadable books of the 20 most interesting problems published each year.