Amazon.com has an extraordinary new feature. You are now able to search words/phrases in the text of books and be referred to the actual pages (scanned from the original).
“Below some of the search results, you’ll see a book excerpt with your search terms highlighted, which indicates that the book’s text is searchable. You can either click to see a list of all references to the term in that particular book or click on the excerpt’s page number to read the entire page on which the excerpt appears. Once you’re on a reader page, you can browse forward or back two pages within the book, or you can search the book for other terms.”
So far, you can browse 33 million pages worth of material from 120,000 books.