Gutenberg Project: <Project Gutenberg Index >

Project Gutenberg, abbreviated as PG, is a volunteer effort to digitize and archive cultural works, to "encourage the creation and distribution of eBooks." Founded in 1971 by Michael S. Hart, it is the oldest digital library. Most of the items in its collection are the full texts of public domain books. The project tries to make these as free as possible, in long-lasting, open formats that can be used on almost any computer. As of December 2009, Project Gutenberg claimed over 30,000 items in its collection. Project Gutenberg is affiliated with many projects that are independent organizations which share the same ideals, and have been given permission to use the Project Gutenberg trademark.
Wherever possible, the releases are available in plain text, but other formats are included, such as HTML, PDF, EPUB, MOBI, and Plucker. Most releases are in the English language, but many non-English works are also available. There are multiple affiliated projects that are providing additional content, including regional and language-specific works. Project Gutenberg is also closely affiliated with Distributed Proofreaders, an internet-based community for proofreading scanned texts.

wikisource 維基文庫: ＜http: //zh.wikisource.org/zh-hant/Wikisource:首页＞

Wikisource collects and stores in digital format previously published texts; including novels, non-fiction works, letters, speeches, constitutional and historical documents, laws and a range of other documents. All texts collected are either free of copyright or released under the Creative Commons Attribution/Share-Alike License. Texts in all languages are welcome, as are translations. Almost 100,000 chinese literal works are hosted in 2010.
Wikisource does not host "vanity press" books or documents produced by its contributors.

Google Books:  <http://books.google.com.hk/books>

Google Books (previously known as Google Book Search and Google Print) is a service from Google that searches the full text of books that Google has scanned, converted to text using optical character recognition, and stored in its digital database. The service was formerly known as Google Print when it was introduced at the Frankfurt Book Fair in October 2004. Google's Library Project, also now known as Google Book Search, was announced in December 2004.

The Google Books database continues to grow. For users outside the United States, though, Google must be sure that the work in question is indeed out of copyright under local laws. According to a member of the Google Books Support Team, "Since whether a book is in the public domain can often be a tricky legal question, we err on the side of caution and display at most a few snippets until we have determined that the book has entered the public domain." Users outside the United States can however access a large number of public domain books scanned by Google using copies stored on the Internet Archive.
Many of the books are scanned using the Elphel 323 camera at a rate of 1,000 pages per hour.
The initiative has been hailed for its potential to offer unprecedented access to what may become the largest online corpus of human knowledge and promoting the democratization of knowledge, but it has also been criticized for potential copyright violations.

Universal Digital Library(UDL)「環球數位圖書館」: <http://www.ulib.org/>

The Million Book Project (or the Universal Library), is a book digitization project, led by Carnegie Mellon University School of Computer Science and University Libraries. Working with government and research partners in India and China, the project is scanning books in many languages, using OCR to enable full text searching, and providing free-to-read access to the books on the web. As of 2007, they have completed the scanning of 1 million books and have made accessible the entire database from <http://www.ulib.org>.

wenty-two scanning centers are operating in India, including four mega-centers. Eighteen centers are running in China, including a mega-center in a free-trade zone to avoid customs delays with shipments of books from the United States. Materials are also being scanned in Egypt, Hawaii, and Carnegie Mellon.
By December 2007 more than 1.5 million books have been scanned, in 20 languages: 970,000 in Chinese; 360,000 in English; 50,000 in Telugu; and 40,000 in Arabic. Most of the books are in the public domain, but permission has been acquired to include over 60,000 copyrighted books (roughly 53,000 in English and 7,000 in Indian languages). The books are mirrored in part at sites in India, China, Carnegie Mellon, the Internet Archive, Bibliotheca Alexandrina. The books that have been scanned to date are not yet all available online, and no single site has copies of all the books that are available online.