Link: http://books.google.com/

So...have you discovered Google Books yet?

If you haven't you need to give it a try! This is so cool! You can access Google Books by typing the address, http://books.google.com directly into your address bar or by running across it during a routine search.

Follow up:

Let me give you an example.
I just searched for "Cornwall, VT" and genealogy. On page one of the search the search result Field Genealogy: Being the Record of All the Field Family in ... - Google Books Result was returned. OK...so it's a link...go ahead and click it!

Told you it was cool! Google is digitizing all sorts of books...especially many older and out of print editions which is fantastic for genealogists. What's even better though is the fact that when a book's copyright expires...the entire book is available for download. This is a phenomenal concept and one I'll be using on a regular basis.