This guide provides information about Open Educational Resources, or OER, including how to find and evaluate them.

- American Institute of Mathematics (AIM) - Approved Open TextbooksThis site provides a list of open textbooks approved for use by the American Institute of Mathematics.

- MyOpenMathAre you an instructor who wants to adopt an open textbook, who feels online interactive homework is valuable, but doesn't want their students to have to pay an additional fee? Then read more about using MyOpenMath in the classroom.
- SageSageMath is a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more. Access their combined power through a common, Python-based language or directly via interfaces or wrappers.
- GraspleAn online platform for instructors to collaboratively create and share open exercises and lessons for Math and Statistics. Includes interactive exercises for Prealgebra, Calculus, Linear Algebra, and Statistics.
- Lumen Online Homework ManagerDesigned by educators, Lumen Online Homework Manager (OHM) draws from thousands of interactive assessment questions to help students master math and other quantitative skills.
- MIT MathletsThe MIT Mathlets constitute a suite of carefully designed and highly interactive Javascript applets designed to enhance selected university level STEM classes.
- GeoGebraGeoGebra is dynamic mathematics software for all levels of education that brings together geometry, algebra, spreadsheets, graphing, statistics and calculus in one easy-to-use package. GeoGebra is a rapidly expanding community of millions of users located in just about every country.
- DesmosDesmos includes multiple tools for use in mathematics courses, including the HTML5 Desmos graphing calculator, which millions of students around the world use for free, including students who are blind or visually-impaired. They also provide teaching activities and an activity builder for instructors using the platform.
- Math InsightThe Math Insight web site is a collection of pages and applets designed to shed light on concepts underlying a few topics in mathematics. The focus is on qualitative description rather than getting all technical details precise.
- CoCalcA spinoff from the open source Sagemath, Co Calc offers a platform-specific edition of Jupyter notebooks with real-time collaboration, chat, and precise edit-history, an extensive Python stack, and additional resources for users. To integrate into a course, this requires a payment of ~$5 per student.
- WebWork Open Problem LibraryThe WeBWorK Open Problem Library (OPL) contains problems contributed by faculty from many institutions that have used WeBWorK, an open-source online homework system for math and sciences courses. WeBWorK is supported by the MAA and the NSF. Currently, there are approximately 35,000 problems in the OPL, and new problems are added regularly.

- Book of ProofThis book will initiate you into an esoteric world. You will learn and apply the methods of thought that mathematicians use to verify theorems, explore mathematical truth and create new mathematical theories. This will prepare you for advanced mathematics courses, for you will be better able to understand proofs, write your own proofs and think critically and inquisitively about mathematics.
- A Gentle Introduction to the Art of MathematicsA Gentle Introduction to the Art of Mathematics (GIAM for short) is a textbook for a "transitions" course. Transitions courses (also known as "foundations" or "intro to proofs" courses) are typically taken after the Calculus sequence and before upper-division coursework in the mathematics major. Their purpose is to acclimatize the student to some of the culture and terminology of mathematics and to begin developing in them a proficiency at reading and writing mathematical proofs.
- Mathematics for the Liberal ArtsThis course was originally developed for the Open Course Library project. The text used is Math in Society, edited by David Lippman, Pierce College. Topics covered in the course include problem solving, voting theory, graph theory, growth models, finance, data collection and description, and probability.
- Quantitative Problem Solving in Natural ResourcesFunded through the ISU Miller Open Education Mini-Grant Program, this text is intended to support courses that bridge the divide between mathematics typically encountered in U.S. high school curricula and the practical problems that natural resource students might engage with in their disciplinary coursework and professional internships.

- OpenStax PrealgebraPrealgebra is a textbook for a one-semester course that serves as a bridge between arithmetic and algebra. It can be used in courses named “Basic Mathematics,” “Introductory Algebra,” “Fundamentals of Algebra,” and so on. The organization makes it easy to adapt the book to suit a variety of course syllabi.
- OpenStax Elementary AlgebraElementary Algebra is designed to meet the scope and sequence requirements of a one-semester elementary algebra course. The book’s organization makes it easy to adapt to a variety of course syllabi. The text expands on the fundamental concepts of algebra while addressing the needs of students with diverse backgrounds and learning styles.
- OpenStax Algebra and TrigonometryAlgebra and Trigonometry provides a comprehensive and multi-layered exploration of algebraic principles. The text is suitable for a typical introductory Algebra & Trigonometry course, and was developed to be used flexibly. The modular approach and the richness of content ensures that the book meets the needs of a variety of programs.
- OpenStax Intermediate AlgebraIntermediate Algebra is designed to meet the scope and sequence requirements of a one-semester intermediate algebra course. The book’s organization makes it easy to adapt to a variety of course syllabi. The text expands on the fundamental concepts of algebra while addressing the needs of students with diverse backgrounds and learning styles.

- A First Course in Linear AlgebraThis text, originally by Ken Kuttler, has been redesigned by the Lyryx editorial team as a first course in linear algebra for science and engineering students who have an understanding of basic algebra. All major topics of linear algebra are available in detail, as well as proofs of important theorems.
- Linear Algebra with ApplicationsThe aim of the text is to achieve a balance among computational skills, theory, and applications of linear algebra. It is a relatively advanced introduction to the ideas and techniques of linear algebra targeted for science and engineering students who need to understand not only how to use these methods but also gain insight into why they work.
- Linear Algebra with Applications: An adaptation for MAT223 UTMThis open textbook is an adaptation of Linear Algebra with Applications by W. Keith Nicholson. The original book can be found and downloaded from Lyryx.com. Five topics are covered here: system of linear equations, matrix algebra, determinants and diagonalization, vector geometry and vector space. It's suitable for beginners who are interested in learning linear algebra.
- Linear Algebra: A Course for Physicists and EngineersThis open textbook is meant for courses on space and atmospheric science, remote sensing, geographic information systems, meteorology, climate and satellite communications. Various applications of formal theory are discussed as well, including differential equations, statistics, optimization and some engineering-motivated problems in physics.

- Topics in PrecalculusIn addition to re-enforcing content from algebra such as exponential and logarithmic functions, and complex numbers, this book introduces the reader to more novel concepts by investigating in detail two of the most basic shapes in geometry: the circle and the triangle.
- OpenStax PrecalculusPrecalculus is adaptable and designed to fit the needs of a variety of precalculus courses. It is a comprehensive text that covers more ground than a typical one- or two-semester college-level precalculus course. The content is organized by clearly-defined learning objectives and includes worked examples that demonstrate problem-solving approaches in an accessible way.
- OpenStax CalculusCalculus is designed for the typical two- or three-semester general calculus course, incorporating innovative features to enhance student learning. The book guides students through the core concepts of calculus and helps them understand how those concepts apply to their lives and the world around them. Volume 1 covers functions, limits, derivatives, and integration.
- Contemporary Calculus IThis is a textbook for differential calculus with explanations, examples, worked solutions, problem sets and answers. It has been reviewed by calculus instructors and class-tested by them and the author.
- Applied CalculusAn openly licensed applied calculus textbook, covering derivatives, integrals, and an intro to multivariable calculus. This book is heavily remixed from Dale Hoffman's Contemporary Calculus textbook, and retains the same conceptual focus from that text.
- Active Calculus MultivariableIn Active Calculus Multivariable, we endeavor to actively engage students in learning the subject through an activity-driven approach in which the vast majority of the examples are completed by students. Where many texts present a general theory of calculus followed by substantial collections of worked examples, we instead pose problems or situations, consider possibilities, and then ask students to investigate and explore.
- Community CalculusAn early transcendentals book covering single variable calculus, infinite series, and multivariable calculus.
- Calculus: Early TranscendentalsThis approachable text provides a comprehensive understanding of the necessary techniques and concepts of the typical Calculus course sequence, and is suitable for the standard Calculus I, II and III courses. To practice and develop an understanding of topics, this text offers a range of problems, from routine to challenging, with selected solutions.
- Differential Calculus for the Life SciencesIn this textbook, the applications form an important focal point, with emphasis on life sciences. This places the techniques and concepts into practical context, as well as motivating quantitative approaches to biology taught to undergraduates. While many of the examples have a biological flavour, the level of biology needed to understand those examples is kept at a minimum.

- Basic Analysis: Introduction to Real AnalysisThis is exactly the material that a student needs to see in their first two semesters of introductory analysis. It can be used as a first proof-based course coming after a linear algebra or possibly concurrently. Different people will find it fitting their curriculum differently. But this book provides a very nice two semester course that starts by introducing set theory and induction for the first time and ends with students ready for topology, measure theory, or more advanced calculus.
- Elementary Differential Equations with Boundary Value ProblemsElementary Differential Equations with Boundary Value Problems is written for students in science, engineering, and mathematics who have completed calculus through partial differentiation. If your syllabus includes Chapter 10 (Linear Systems of Differential Equations), your students should have some preparation in linear algebra.
- Spiral Workbook for Discrete MathematicsThis is a text that covers the standard topics in a sophomore-level course in discrete mathematics: logic, sets, proof techniques, basic number theory, functions, relations, and elementary combinatorics, with an emphasis on motivation. It explains and clarifies the unwritten conventions in mathematics, and guides the students through a detailed discussion on how a proof is revised from its draft to a final polished form.
- Combinatorics Through Guided DiscoveryThis book is an introduction to combinatorial mathematics, also known as combinatorics. The book focuses especially, but not exclusively, on the part of combinatorics that mathematicians refer to as "counting." The book consists almost entirely of problems. Some of the problems are designed to lead you to think about a concept, others are designed to help you figure out a concept and state a theorem about it, while still others ask you to prove the theorem. Above all, this book is dedicated to the principle that doing mathematics is fun.