There are many useful, and many more useless, things on the Web. It is important to be discriminating in your use of this resource for academic work (and for the purposes of essay writing, sources from the web should be cited as ordinary bibliographical items).

Recommended as a starting point are: Argos - a search engine specifically geared to Classical sites on the Internet

Perseus Project: includes texts (Greek and Latin) with translations and commentaries, an archive of images of Greek vases and an encyclopaedia and bibliographic resource.