So this has come up on a few of my groups, and I thought since I did one on Irish Language resources I would do one for online resources to reliable sites to Celtic mythology.
Celtic Digital Initiative: (from their website) The aim of the Celtic Digital Initiative (CDI) is to make scarce
resources available in an electronic format to students and scholars,
both within UCC and beyond.
Mary Jones: (From their website) This is an attempt to collect as many possible early and medieval texts
produced in the "Celtic" countries, or on Celtic themes (hence the
inclusion of Continental Arthurian works). Some works are actually
links off-site; others are provided here at the CLC.
Corpus of Electronic Texts (CELT): (From their website) To bring the wealth of Irish literary and historical culture (in Irish,
Latin, Anglo-Norman French, and English) to the Internet in a
rigorously scholarly and user-friendly project for the widest possible
range of readers and researchers. CELT (the Corpus of Electronic Texts)
caters for academic scholars, teachers, students, and the general
public, all over the world.
A Corpus of Ancient Written References to the Druids: Note I am only recommending this page of the website as I have not read the rest of it. (From the website) First of all, these are primary sources, not secondary sources. In other
words, these ancient records are to a large extent the basis of our
knowledge about the Druids. This means that by becoming familiar with
them and understanding them, one can gain a more direct and firmer
familiarity with the subject matter than by merely consulting modern
works, which are, after all, derived from them. Often one can
demonstrate by referring to them that a statement regarding the Druids
in a modern work is false or unwarranted. On the other hand, this also
means that these sources are not critical or scientific works - the
Greeks, Romans and Church Fathers who authored them were not impartial
and usually did not have good information about the Druids. Therefore,
not everything they wrote about them was necessarily true. These are
texts to be analyzed, not simply believed at face value. This is an
important point, so I will say it again in bold: These are texts to be analyzed, not simply believed at face value.
Sacred Texts: I don't think this site needs an introduction.
Alexei Kondratiev's Celtic Story Telling: A series of six Youtube videos, where Alexei talks about Celtic Story telling.