Open Textbook Initiative. The The American Institute of Mathematics (AIM) has developed evaluation criteria to identify the open source textbooks that are suitable for use in traditional university courses. The Editorial Board maintains a list of approved textbooks which have been judged to meet these criteria.
UTMOST: Undergraduate Teaching in Mathematics with Open Software and Textbooks. The UTMOST project is an NSF IUSE grant focusing how students understand and faculty actually use textbooks in undergraduate mathematics courses. UTMOST will use this understanding to produce textbooks that are more effective in promoting student learning. The major components of the project involve education research, resource development, dissemination, and evaluation.
UTMOST Sage Cell Repository. The Sage cell repository is a highly structured catalog of reusable Sage cells that can be easily embedded into online documents. Each Sage cell is tagged with important attributes to make it easy for instructors, authors, and anyone using Sage to find examples of Sage code appropriate for their needs. The Sage Cell repository is being jointly developed with the National Science Foundation sponsored project Curated Courses. Below is an example of a Sage cell that plots a sine curve.
PreTeXt (formerly MathBook XML) is a lightweight XML application for authors of scientific articles, textbooks and monographs that incorporates the best of DocBook, LaTeX, and HTML. When a document is written in PreTeXt, it is possible to quickly produce print, PDF, web, HTML, Sage Notebooks, Jupyter Notebooks, and even Braille from a single source.