The Online Books Page, maintained by the University of Pennsylvania, is a web site that facilitates access to books that are available over the Internet. It includes an index of thousands of online books freely readable on the Internet, plus directories and pointers to other archives.http://onlinebooks.library.upenn.edu/aboutolbp.html
Project Gutenberg is the Internet's oldest producer of free electronic books. The Project Gutenberg Philosophy is to make information, books and other materials available to the general public in forms a vast majority of the computers, programs and people can easily read, use, quote, and search. www.gutenberg.org/
USGenWeb Special Collections provides an entry page to scanned out-of-print books on family studies, historical books and various journals permanently stored in the USGenWeb Archives for free access. Included here is the well known William & Mary Quarterly, and the Chronicles of the Scotch-Irish in Virginia, as well as many others. http://www.rootsweb.com/~usgenweb/special/
The American Colonist's Library is a site focused on primary source documents pertaining to early American history. A valuable collection of historical works which contributed to the formation of American politics, culture, and ideals. You probably won’t find a book about your ancestors in this collection, but you will find the books your ancestors read and lived by.
The Early Americas Digital Archive at the University of Maryland is a collection of electronic texts and links to texts originally written in or about the Americas from 1492 to approximately 1820.http://www.mith2.umd.edu/eada/
Google Books (previously known as Google Book Search and Google Print) is a service from Google Inc. that searches the full text of books and magazines that Google has scanned, converted to text using optical character recognition, and stored in its digital database. Results from Google Books show up in both Google Web Search and the dedicated Google Books site (books.google.com). A click on a result from Google Books opens an interface in which the user may view pages from the book, if out of copyright or if the copyright owner has given permission. Books in the public domain are available in "full view" and free for download. For in-print books where permission has been granted, the number of viewable pages is limited to a "preview".