TEDTalks presentation by Richard Baraniuk:
There are misconceptions that all Open Textbooks are "low quality" materials because they are free, but most do undergo a peer review process. The following links describe some of the evaluation criteria to which open textbooks are subject:
The BC Campus Open Textbook Project is Canada's first government-funded project of its kind, and has been tasked with the ongoing creation of open textbooks for the province’s public post-secondary system. The texts are available for free online or through low-cost print versions. BC Campus provides updated lists of these textbooks as more become available.
The following is a list of prominent open textbook collections. See the list of OER Repositories to find many more open textbooks.