I know many people like me love books, sometimes we run out of money to buy a good book on these sites desribire in this post you can get free.
1. Repository of the United Nations (35,000 posts): It features more than 8,000 authors in 5 languages, which can be consulted and downloaded. Among all the material you may find institutional books, annual reports, series, magazines, newsletters, conference papers and meetings, as well as multimedia resources.
This repository is created by the United Nations Economic Commission for Latin America and the Caribbean (ECLAC). Log in with http://repositorio.cepal.org/
2. School of Journalism (+100 posts): This web site is created by journalist Esther Vargas from Peru, provides information of interest to students of journalism and media; has an interesting digital library, from which you can view and download manuals and related to the field of journalism and social communication books. Log in with http://www.clasesdeperiodismo.com/biblioteca-digital/
3. Virtual Library Miguel de Cervantes (130,000 posts): This library began its development in 1998, making its launch in December 2000. It is a commitment to provide digitally fundamental works of culture in Spanish, especially those that have been created in Spain and Latin America. Log in with http://www.cervantesvirtual.com/
4. Wikisource (90,000 pages); This is a Wikimedia project, the same organization responsible for Wikipedia. The intention of this website is to provide the content of texts that are public domain or have been released under a license that allows free distribution, such as the GPL or Creative Commons.
The books can be viewed directly on the website or it is possible to download in PDF format. Wikisource currently has 98,494 items in Spanish language, and this number increases every day. Log in with http://es.wikisource.org/wiki/Portada
6. Comic Book Plus (+25.000 comics): I also thought comic lovers (I like some), especially those who like the old comics. To you we recommend a place where you will find over 25,000 comics golden era (1930 to 1950 with Superman, Batman, Captain America …) and silver (1956, The Flash, Spiderman …).
It is noteworthy that although the most famous comics are not, having all rights reserved; a good amount of material that time already under public domain and available Comic Book Plus. Sign in http://comicbookplus.com/?cid=1732
7. GitHub (+500 books): GitHub is a tool to host software projects, and thanks to community have formed large repositories with lots of books on topics related to software development. Some of these books are available for consultation via the web and others to be downloaded. Find books in English https://github.com/vhf/free-programming-books/blob/master/free-programming-books.md#git
8. Blog Media 8 (+500 books): People of this website has created a list of books on communication, internet, social networking and web 2.0 we can download. The material is in Spanish (97 books), English and Portuguese. Log in with http://blogmidia8.com/biblioteca-virtual-html
9. Public Domain: This website disseminates public domain works, it catalog includes works mainly in Spanish, but it is also possible to find other works in Portuguese, Italian, English, Swedish, Latin and German. Login http://www.dominiopublico.es/
Google Books (+20.0000.0000 books): This tool is not for downloading books themselves, but it lets see a preview of millions of books that have been added to its catalog. Although the total number of pages that are displayed for each book is limited by license, consider its mention, since it can be very useful if we see a few pages of a book before buying it. Login http://books.google.es/
I hope this list will be useful, and if you know more places where legally download books, please leave me a comment.