Okay, I know that Hogwarts is in Scotland and they don't celebrate Thanksgiving. But let's pretend, shall we?
1.) Most Puffs go home to their families, but a small group always stays so the people who aren't going home won't be alone
2) Muggleborn (and sometimes half blood) Puffs Skype each other over vacation, and the Purebloods are very confused about what this "Skype" is.
3) Debate about whether they can eat both ham and turkey and still be hungry for dessert
4) Decorate the common room with golden lights, fall leaves, and pumpkins
5) One Hufflepuff stays out all day, returns holding a turkey, and all the Hufflepuffs play a lively Irish game called "Catch the Turkey"
6) Hufflepuffs helping each other with their homework, because they want to get it done before thanksgiving break.
7) Hufflepuffs dressing up in bright yellow clothes, holding the banners and the awards that Hufflepuff has won over the years, and singing good-bye to the people who are leaving on the train
8) The Hufflepuffs who stayed back baking cookies and giving them out to the other houses.
9) Letting Frank the turkey go, with teary eyes
10) Sing the entire train ride home