If you don't celebrate anything at this time, or want to know about other celebrations, here are some references:
http://en.wikipedia.org/wiki/Inti_Raymi
http://en.wikipedia.org/wiki/Bodhi_Day
http://en.wikipedia.org/wiki/Winter_solstice#Mean_Geimrech_.28Celtic.29
http://en.wikipedia.org/wiki/Constitution_of_the_Republic_of_China
http://en.wikipedia.org/wiki/Advent
http://en.wikipedia.org/wiki/Saint_Nichola http://en.wikipedia.org/wiki/Christmas_Eve
http://en.wikipedia.org/wiki/Christmas
http://en.wikipedia.org/wiki/Twelve_Days_of_Christmas
http://en.wikipedia.org/wiki/Saint_Stephen
http://en.wikipedia.org/wiki/Saint_John_the_Evangelist
http://en.wikipedia.org/wiki/Holy_Innocents
http://en.wikipedia.org/wiki/Sylvester_I
http://en.wikipedia.org/wiki/Watch_Night
http://en.wikipedia.org/wiki/Feast_of_the_Circumcision
http://en.wikipedia.org/wiki/Feast_of_Fools
http://en.wikipedia.org/wiki/Saint_Basil
http://en.wikipedia.org/wiki/Twelfth_Night_%28holiday%29
http://en.wikipedia.org/wiki/Epiphany_%28feast%29
http://en.wikipedia.org/wiki/Winter_solstice#Modranicht.2C_Modresnach_.28Anglo-Saxon.2C_Germanic.29
http://en.wikipedia.org/wiki/Yule
http://en.wikipedia.org/wiki/Hanukkah
http://en.wikipedia.org/wiki/Sadeh
http://en.wikipedia.org/wiki/Yalda
http://en.wikipedia.org/wiki/Chahar_Shanbeh_Suri
http://en.wikipedia.org/wiki/Saturnalia
http://en.wikipedia.org/wiki/Dies_Natalis_Solis_Invicti
http://en.wikipedia.org/wiki/Koleda
http://en.wikipedia.org/wiki/Malanka
http://en.wikipedia.org/wiki/Maslenitsa
http://en.wikipedia.org/wiki/Zamenhof_Day
http://en.wikipedia.org/wiki/HumanLight
http://en.wikipedia.org/wiki/Boxing_Day
http://en.wikipedia.org/wiki/Kwanzaa
http://en.wikipedia.org/wiki/Hogmanay
http://en.wikipedia.org/wiki/New_Year%27s_Day