I recently made a similar thread, so most things I learned this year can be found there: www.elitefourum.com/t/random-pokemon-related-til-moments/21493/1
I indeed agree with the ©1999-2000 Australian Fossil print run and Ancient Mew variations. I now know about them for quite a while, but those were indeed some exciting new pieces of information I learned after joining the E4 forum. The ©1999 and ©1999-2000 Spanish Base Set differences or German Fliegendes Pikachu vs Flug-Pikachu were also pretty exciting for me personally. 
Even though I’ve been part of the E4 community for almost three years now, I think there isn’t a month in which I don’t learn something new, which is also one of the big reasons why I still enjoy collecting and being part of this community a lot.
Greetz,
Quuador