New book - 'Building a Better World in Your Backyard' - on Kickstarter (sponsored friend)
Open source textbooks
OpenStax College offers students free textbooks that meet scope and sequence requirements for most courses. These are peer-reviewed texts written by professional content developers. Adopt a book today for a turnkey classroom solution or modify it to suit your teaching approach. Free online and low-cost in print, OpenStax College books.
They print in cc-by.