CK12 is a great resource for students and teachers. Their flexbook site contains tons of online textbooks, all free, for teachers to use. You can also create your own flexbook on the site, combining parts of other textbooks from their site, or using materials of your own. Books are available in PDF, Kindle, iPad, NOOK and other formats.
In February, they reached 1,000,000 books downloaded, showing how popular open, e-textbooks are becoming.
They also have content: US History Sourcebook - basic, available in ePub format (readable on iOS, Android and NOOK.
The FlexBooks system will be getting updated to version 2.0 soon, which will "combine student-centric learning with teacher-centric tools and materials to create a dynamic system." Invitation only beta testing will be starting this month. New titles that will be released soon include:
CK-12 Algebra II w/Trig (the first five chapters)
CK-12 Middle School Math - Grade 6, Teacher's Edition, Teaching Tips
CK-12 Middle School Math - Grade 6, Teacher's Edition, Common Errors
CK-12 Middle School Math - Grade 6, Teacher's Edition, Differentiated Instruction
CK-12 Physical Science For Middle School
In addition to the Flexbooks digital textbooks, CK-12 offers free SAT prep and an interactive Algbra curriculum.
This is a great resource for all educators and students. To use e-textbooks, students have to have access to technology, which costs money. Free and open e-textbooks are a great way to save money.
Related:
eTextbooks, Textbooks, iPads - what are the costs?
Apple Announces iBooks2 E-Textbooks - my initial thoughts
