Economics textbooks free and online

Bookboon.com
Bookboon.com is a publisher of free ebooks. The site contains a plethora of books in various subjects; the primary focus, however, is on economics, business, IT and engineering. All books are in PDF format. The books are authoritative original works, primarily written by college and university professors, with the express permission to be published only by bookboon.com. To handle costs of publishing and reviewing books and of course author fees, the books contain advertisement on every third page. Read more at the Wikipedia article or Campus Techonology

Textbookrevolution
Textbookrevolution provides a ample collection of links to other providers of ebooks, including but not limited to Bookboon. It is run by students, and dedicated to the spread of free learning materials in education.