The Directory of Open Access Books (DOAB) provides a searchable index to peer-reviewed monographs and edited volumes published under an Open Access business model, with links to the full texts of the publications at the publisher’s website or repository.
Athabasca University Press was the first university in Canada to create an open access scholarly press. Access to all AU Press publications is free over the Internet.
Open Humanities Press (OHP) is an international open access publishing collective whose mission is to make leading works of contemporary critical thought freely available worldwide. All publications are peer-reviewed.
Ubiquity Press is a fully open access publisher. They publish both individual and series books, all fully peer reviewed, and also support other university presses with the transition to e-publishing.
Open Book Publishers is a non profit organization that publishes books in hardback, paperback, pdf and ebook editions, but they also include a free online edition that can be read via their website, downloaded, reused or embedded anywhere.
OAPEN (Open Access Publishing in European Networks) is a collaborative initiative to develop and implement a sustainable Open Access publication model for academic books in the Humanities and Social Sciences.
A collaborate initiative enabling open access books, the Knowledge Unlatched model depends on many libraries from around the world sharing the payment of a single Title Fee to a publisher, in return for a book being made available on a Creative Commons licence via OAPEN and HathiTrust as a fully downloadable PDF.
From the Unglue.it "About" page:
At Unglue.it, you can pledge toward creating ebooks that will be legally free, worldwide. These books have already been traditionally published, but they're stuck: legal restrictions keep you from being able to enjoy and share them.
Unglue.it gets them unstuck. Authors and publishers decide what amount lets them freely share their books with the world while still making a living. We raise that fee here through crowdfunding: people like you chipping in. When campaigns succeed, the rights holders get paid, and they issue a free electronic edition under a Creative Commons license.