A lot of Greek and Latin texts are available on the internet in the form of digital facsimiles --- page images of printed books or manuscripts. Digital facsimiles are useful both in research and in teaching (especially facsimiles of old printed books, of papyri, of medieval and early modern manuscripts). Such facsimiles can be addenda to, or even an interim solution for, re-publication of rare titles and works.
Bibliographies of digital facsimiles
A meta-bibliography of collections of digital facsimiles is compiled by the British Library: .
An example of good practice in serving digital facsimiles freely accessible over the internet is the Digitale Bibliothek of the Bayerische Staatsbibliothek.
Compiling own lists of digital facsimiles
Specialized lists of titles accessible through these service and important for classicists, can (and should be) compiled and shared, e. g. as contributions to Wikisource (cf. the list of volumes of Hermes. Zeitschrift für classische Philologie compiled on German Wikisource), or to social bookmark and publication sharing services such as BibSonomy.