As some of you might have noticed, a lot of games have been updated recently having few or no patchnotes, but some new achievements added.
So it's only natural to expect another event along with the obligatory winter sale. Of course, that would be a lot of time to spend if you have many of those games, so you might want to start early, since there are some achievements already obtainable.
I found this list online:
http://forums.steampowered.com/forums/showthread.php?t=2272641
