Public Domain Books

Public Domain Books Collections

Project Gutenberg

There are nearly 30,000 free books in the Project Gutenberg Online Book Catalog. A grand total of over 100,000 titles are available at Project Gutenberg Partners, Affiliates and Resources. Readers outside of the United States: check copyright laws of your country before downloading or redistributing eBooks.
Project Gutenberg

Authorama

Features books from a variety of different authors, collected here for you to read online or offline.
Authorama

Google Books

From the Big Daddy of the Internet. Not sure about the all inclusive nature of the public domain here, but Google is King and there are books and applications to read them with. Going to download GoogleBooks to my iphone right now!
Google Books