Not much from what I seen
I only play on ACR, 888 and PokerStars (listed as I prefer them
).
ACR has ZERO holiday freerolls. Some of the radio stations have special holiday events but they are all buy-in tournaments (micro to low). However, this is still by-far my favorite site. I just find the overall quality of players is better and less bingo players (however, it is starting to get worse as it grows in popularity).
888 had the $1000 Merry Xmas Freeroll running 3x daily leading up to Christmas and now the $1000 New Years Freerolls running 3x daily leading up to New Years. I tend to only go to 888 if I am bored and there is nothing going on at ACR.
PokerStars is a bust for me all around. I can never find any freerolls to play other than the CC ones and I really don't like their software so I tend to only play league games there. Maybe it's because I have never deposited at PokerStars, but I don't see that they have much to offer.