I was wondering if anyone here knew of any sources of the Fathers (specifically St. John Chrysostom) in the original Greek, either in book form or online format. I have a few volumes of the Post-Nicene and Nicene Fathers and would like to see the original Greek. I'd be greatly appreciative of this! Thank you.
For many centuries, Migne was the main source. You can still use his editions if you want, but, nowadays there are many series that publish critical texts. Just Google "Corpus Christianorum" or "Sources Chrétiennes" - those are the best series. Also, you could check out the Thesaurus Linguae Graecae for some free versions online:
http://www.tlg.uci.edu/demoinfo/demoauthors.php