These are two related initiative that can be a great help when trying to do a little research form the comfort of ones own computer.
Archive.org contains the Wayback Machine which archives snap shot of websites. You can thus see pages on websites as they used to be. However, archive.org also contains free and complete copies of many books that are out of copyright and in the public domain.
Openlibrary.org aims to get “One web page for every book ever published”. You can search for the details of any book here and using the “Only show ebooks” option easily find free copies of old books.