As of today, the holiday events I found so far are:

CoH
Longbow Reservists Badge and temporary fly power for logging in.
badge and Santa hat for mish (don't know name of badge)
opportunity for heroes to earn the wolf spider and fortunata badges as these spawn in the santa hat mish.

CoV
Jet-setter badge and temporary fly power for logging in.
Scrooge badge and a santa hat for a mish with 4 glowies in it


I got an email from NCSoft mentioning something about going onto enemy territory on the 19th so we'll see what else they add.

edit: spent some time getting the holiday mish badge for all my toons. heh lucky that I had a bunch of low levels so I just used their mish and had a guy that was at least 5 levels higher run through and grab the glowies.
also farmed the mish a bit with a full team to try to get the defeat badges but never got them so I'm either thinking the reqs are higher than I thought or you don't get credit for them in this mish.