I have been giving this some thought today, Wicca is a mystery tradition and as such has certain mysteries within it that you witness at the appropriate time. Such mystery traditions existed in the classical world: the Eleusinian Mysteries being the one that springs to mind most prominently. Then of course you have cults such as that of Mithras which also had specific mysteries. A key thing is that these mysteries had to be experienced rather then be explained or talked about, presumably because the effect was in the experiencing, something i can certainly relate to with respect to Wicca.
So, i got to thinking abut what might be called the British or Brythonic mysteries. One I'm told I'm on the track of was with regard to Aranrot; I mentioned some 'thoughts' to someone more experienced and knowledgeable on the matter and he said i was on my way to figuring out one of the British Mysteries. I have ideas about it but haven't yet gone further down that line of inquiry either with him or Aranrot.
So I got to thinking about the value of what the mysteries could be, especially considering that there is unlikely to be some sort of larger cult forming in the foreseeable future. So, one option would be to explain them whether in print or digital format. Alternatively lead people to the experience directly - though this is VERY limiting in the sense that there might not even be a pool of people willing to do this, also, do you lead just anybody and everybody to the experience?
Then of course - what ARE the mysteries?
Dinner needs doing so I will have to come back to this.