Lest anyone get too excited, the Internet Archive is still only an electronic resource and it can only provide an online text or at best a colour PDF. These do not and cannot match an actual physical book. However, when compared to no text at all they are considerably better than nothing. So for those who cannot afford the considerable cost of getting at a print copy of Migne's encyclopaedic collection of the Greek Fathers here are links to much of it in various electronic databases.
Migne - PG