Google Books
http://books.google.com/

Search the full text of Books and find the perfect book for your purposes and discover new ones that interest you. Book Search works just like web search. Try a search on Google Books or on Google.com. When they find a book with content that contains a match for your search terms, they will link to it in your search results. If the book is out of copyright, or the publisher has given them permission, you’ll be able to see a preview of the book, and in some cases the entire text. If it’s in the public domain, you’re free to download a PDF copy. They have created reference pages for every book so you can quickly find all kinds of relevant information: book reviews, web references, maps and more. If you find a book you like, click on the “Buy this book” and “Borrow this book” links to see where you can buy or borrow it. Currently, they are connecting readers with books in two ways: the Partner Program and the Library Project. Check out the new search for magazine content on Google Book search. This has been added to the tools section of Research Resources Subject Tracer™ Information blog. This has been added to Reference Resources Subject Tracer™ Information Blog.