Thanksgiving varies, but I always celebrate it at least twice. *full*
Christmas... My immediate family (including sister and her boyfriend) will exchange gifts in the early morning after some type of breakfast. Fun times.
Then, we'll head out to my step-grandparents' house where all of my step-mom's family is for more food (lunch) and more gifts. There's so many people jammed into one room, it's just funny anymore.
Later, my siblings and I will head to my mother's sister's house for more gifts and more food (dinner). *full* I like my mom's side of the family the best.
Also, I'll definitely be seeing my dad's family sometime around or even on Christmas. That'll be either at my dad's brother's or mother's house. Or both.